* [PATCH qemu v6 1/7] hw/pcie: Support enabling flit mode
2026-02-04 12:12 [PATCH qemu v6 0/7] hw/cxl: Support Back-Invalidate (+ PCIe Flit mode) Jonathan Cameron
@ 2026-02-04 12:12 ` Jonathan Cameron
2026-02-04 12:12 ` [PATCH qemu v6 2/7] hw/cxl: Refactor component register initialization Jonathan Cameron
` (5 subsequent siblings)
6 siblings, 0 replies; 14+ messages in thread
From: Jonathan Cameron @ 2026-02-04 12:12 UTC (permalink / raw)
To: Michael Tsirkin, qemu-devel, Davidlohr Bueso
Cc: linuxarm, linux-cxl, Ravi Shankar, Marcel Apfelbaum,
Markus Armbruster, Michael Roth
From: Davidlohr Bueso <dave@stgolabs.net>
PCIe Flit Mode, introduced with the PCIe 6.0 specification, is a
fundamental change in how data is transmitted over the bus to
improve transfer rates. It shifts from variable-sized Transaction
Layer Packets (TLPs) to fixed 256-byte Flow Control Units (FLITs).
As with the link speed and width training, have ad-hoc property for
setting the flit mode and allow CXL components to make use of it.
For the CXL root port and dsp cases, always report flit mode but
the actual value after 'training' will depend on the downstream
device configuration.
Suggested-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Tested-by: Dongjoo Seo <dongjoo.seo1@samsung.com>
Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
include/hw/cxl/cxl_device.h | 1 +
include/hw/pci-bridge/cxl_upstream_port.h | 1 +
include/hw/pci/pcie.h | 2 +-
include/hw/pci/pcie_port.h | 1 +
hw/mem/cxl_type3.c | 6 ++++--
hw/pci-bridge/cxl_downstream.c | 8 +++++---
hw/pci-bridge/cxl_root_port.c | 8 +++++---
hw/pci-bridge/cxl_upstream.c | 16 +++++++++-------
hw/pci/pcie.c | 23 +++++++++++++++++++----
9 files changed, 46 insertions(+), 20 deletions(-)
diff --git a/include/hw/cxl/cxl_device.h b/include/hw/cxl/cxl_device.h
index d5906afb19a5..7d9236db8c85 100644
--- a/include/hw/cxl/cxl_device.h
+++ b/include/hw/cxl/cxl_device.h
@@ -726,6 +726,7 @@ struct CXLType3Dev {
/* PCIe link characteristics */
PCIExpLinkSpeed speed;
PCIExpLinkWidth width;
+ bool flitmode;
/* DOE */
DOECap doe_cdat;
diff --git a/include/hw/pci-bridge/cxl_upstream_port.h b/include/hw/pci-bridge/cxl_upstream_port.h
index f208397ffe96..e3d6a27acc86 100644
--- a/include/hw/pci-bridge/cxl_upstream_port.h
+++ b/include/hw/pci-bridge/cxl_upstream_port.h
@@ -15,6 +15,7 @@ typedef struct CXLUpstreamPort {
PCIExpLinkSpeed speed;
PCIExpLinkWidth width;
+ bool flitmode;
DOECap doe_cdat;
uint64_t sn;
diff --git a/include/hw/pci/pcie.h b/include/hw/pci/pcie.h
index fc02aeb169f1..0a1cbb8728f3 100644
--- a/include/hw/pci/pcie.h
+++ b/include/hw/pci/pcie.h
@@ -144,7 +144,7 @@ void pcie_ari_init(PCIDevice *dev, uint16_t offset);
void pcie_dev_ser_num_init(PCIDevice *dev, uint16_t offset, uint64_t ser_num);
void pcie_ats_init(PCIDevice *dev, uint16_t offset, bool aligned);
void pcie_cap_fill_link_ep_usp(PCIDevice *dev, PCIExpLinkWidth width,
- PCIExpLinkSpeed speed);
+ PCIExpLinkSpeed speed, bool flitmode);
void pcie_cap_slot_pre_plug_cb(HotplugHandler *hotplug_dev, DeviceState *dev,
Error **errp);
diff --git a/include/hw/pci/pcie_port.h b/include/hw/pci/pcie_port.h
index 7cd7af8cfa4b..53cd64c5edff 100644
--- a/include/hw/pci/pcie_port.h
+++ b/include/hw/pci/pcie_port.h
@@ -58,6 +58,7 @@ struct PCIESlot {
PCIExpLinkSpeed speed;
PCIExpLinkWidth width;
+ bool flitmode;
/* Disable ACS (really for a pcie_root_port) */
bool disable_acs;
diff --git a/hw/mem/cxl_type3.c b/hw/mem/cxl_type3.c
index 85694707e2e4..3c7ecd8c48bc 100644
--- a/hw/mem/cxl_type3.c
+++ b/hw/mem/cxl_type3.c
@@ -405,7 +405,7 @@ static void build_dvsecs(CXLType3Dev *ct3d)
dvsec = (uint8_t *)&(CXLDVSECPortFlexBus){
.cap = 0x26, /* 68B, IO, Mem, non-MLD */
.ctrl = 0x02, /* IO always enabled */
- .status = 0x26, /* same as capabilities */
+ .status = ct3d->flitmode ? 0x6 : 0x26, /* lack of 68B */
.rcvd_mod_ts_data_phase1 = 0xef, /* WTF? */
};
cxl_component_create_dvsec(cxl_cstate, CXL2_TYPE3_DEVICE,
@@ -1315,7 +1315,8 @@ static void ct3d_reset(DeviceState *dev)
uint32_t *reg_state = ct3d->cxl_cstate.crb.cache_mem_registers;
uint32_t *write_msk = ct3d->cxl_cstate.crb.cache_mem_regs_write_mask;
- pcie_cap_fill_link_ep_usp(PCI_DEVICE(dev), ct3d->width, ct3d->speed);
+ pcie_cap_fill_link_ep_usp(PCI_DEVICE(dev), ct3d->width, ct3d->speed,
+ ct3d->flitmode);
cxl_component_register_init_common(reg_state, write_msk, CXL2_TYPE3_DEVICE);
cxl_device_register_init_t3(ct3d, CXL_T3_MSIX_MBOX);
@@ -1354,6 +1355,7 @@ static const Property ct3_props[] = {
speed, PCIE_LINK_SPEED_32),
DEFINE_PROP_PCIE_LINK_WIDTH("x-width", CXLType3Dev,
width, PCIE_LINK_WIDTH_16),
+ DEFINE_PROP_BOOL("x-256b-flit", CXLType3Dev, flitmode, false),
};
static uint64_t get_lsa_size(CXLType3Dev *ct3d)
diff --git a/hw/pci-bridge/cxl_downstream.c b/hw/pci-bridge/cxl_downstream.c
index f7b131e67e8e..64086d8ec2f2 100644
--- a/hw/pci-bridge/cxl_downstream.c
+++ b/hw/pci-bridge/cxl_downstream.c
@@ -94,8 +94,9 @@ static void cxl_dsp_reset(DeviceState *qdev)
latch_registers(dsp);
}
-static void build_dvsecs(CXLComponentState *cxl)
+static void build_dvsecs(PCIDevice *d, CXLComponentState *cxl)
{
+ PCIESlot *s = PCIE_SLOT(d);
uint8_t *dvsec;
dvsec = (uint8_t *)&(CXLDVSECPortExt){ 0 };
@@ -107,7 +108,7 @@ static void build_dvsecs(CXLComponentState *cxl)
dvsec = (uint8_t *)&(CXLDVSECPortFlexBus){
.cap = 0x27, /* Cache, IO, Mem, non-MLD */
.ctrl = 0x02, /* IO always enabled */
- .status = 0x26, /* same */
+ .status = s->flitmode ? 0x6 : 0x26, /* lack of 68B */
.rcvd_mod_ts_data_phase1 = 0xef, /* WTF? */
};
cxl_component_create_dvsec(cxl, CXL2_DOWNSTREAM_PORT,
@@ -182,7 +183,7 @@ static void cxl_dsp_realize(PCIDevice *d, Error **errp)
cxl_cstate->dvsec_offset = CXL_DOWNSTREAM_PORT_DVSEC_OFFSET;
cxl_cstate->pdev = d;
- build_dvsecs(cxl_cstate);
+ build_dvsecs(d, cxl_cstate);
cxl_component_register_block_init(OBJECT(d), cxl_cstate, TYPE_CXL_DSP);
pci_register_bar(d, CXL_COMPONENT_REG_BAR_IDX,
PCI_BASE_ADDRESS_SPACE_MEMORY |
@@ -217,6 +218,7 @@ static const Property cxl_dsp_props[] = {
speed, PCIE_LINK_SPEED_64),
DEFINE_PROP_PCIE_LINK_WIDTH("x-width", PCIESlot,
width, PCIE_LINK_WIDTH_16),
+ DEFINE_PROP_BOOL("x-256b-flit", PCIESlot, flitmode, true),
};
static void cxl_dsp_class_init(ObjectClass *oc, const void *data)
diff --git a/hw/pci-bridge/cxl_root_port.c b/hw/pci-bridge/cxl_root_port.c
index 197d3148d201..5641048084a4 100644
--- a/hw/pci-bridge/cxl_root_port.c
+++ b/hw/pci-bridge/cxl_root_port.c
@@ -104,8 +104,9 @@ static void latch_registers(CXLRootPort *crp)
cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT);
}
-static void build_dvsecs(CXLComponentState *cxl)
+static void build_dvsecs(PCIDevice *d, CXLComponentState *cxl)
{
+ PCIESlot *s = PCIE_SLOT(d);
uint8_t *dvsec;
dvsec = (uint8_t *)&(CXLDVSECPortExt){ 0 };
@@ -126,7 +127,7 @@ static void build_dvsecs(CXLComponentState *cxl)
dvsec = (uint8_t *)&(CXLDVSECPortFlexBus){
.cap = 0x26, /* IO, Mem, non-MLD */
.ctrl = 0x2,
- .status = 0x26, /* same */
+ .status = s->flitmode ? 0x6 : 0x26, /* lack of 68B */
.rcvd_mod_ts_data_phase1 = 0xef,
};
cxl_component_create_dvsec(cxl, CXL2_ROOT_PORT,
@@ -176,7 +177,7 @@ static void cxl_rp_realize(DeviceState *dev, Error **errp)
cxl_cstate->dvsec_offset = CXL_ROOT_PORT_DVSEC_OFFSET;
cxl_cstate->pdev = pci_dev;
- build_dvsecs(cxl_cstate);
+ build_dvsecs(pci_dev, cxl_cstate);
cxl_component_register_block_init(OBJECT(pci_dev), cxl_cstate,
TYPE_CXL_ROOT_PORT);
@@ -211,6 +212,7 @@ static const Property gen_rp_props[] = {
speed, PCIE_LINK_SPEED_64),
DEFINE_PROP_PCIE_LINK_WIDTH("x-width", PCIESlot,
width, PCIE_LINK_WIDTH_32),
+ DEFINE_PROP_BOOL("x-256b-flit", PCIESlot, flitmode, true),
};
static void cxl_rp_dvsec_write_config(PCIDevice *dev, uint32_t addr,
diff --git a/hw/pci-bridge/cxl_upstream.c b/hw/pci-bridge/cxl_upstream.c
index 6d708fadc253..c352d11dc7b7 100644
--- a/hw/pci-bridge/cxl_upstream.c
+++ b/hw/pci-bridge/cxl_upstream.c
@@ -101,28 +101,29 @@ static void cxl_usp_reset(DeviceState *qdev)
pci_bridge_reset(qdev);
pcie_cap_deverr_reset(d);
- pcie_cap_fill_link_ep_usp(d, usp->width, usp->speed);
+ pcie_cap_fill_link_ep_usp(d, usp->width, usp->speed, usp->flitmode);
latch_registers(usp);
}
-static void build_dvsecs(CXLComponentState *cxl)
+static void build_dvsecs(CXLUpstreamPort *usp)
{
+ CXLComponentState *cxl_cstate = &usp->cxl_cstate;
uint8_t *dvsec;
dvsec = (uint8_t *)&(CXLDVSECPortExt){
.status = 0x1, /* Port Power Management Init Complete */
};
- cxl_component_create_dvsec(cxl, CXL2_UPSTREAM_PORT,
+ cxl_component_create_dvsec(cxl_cstate, CXL2_UPSTREAM_PORT,
EXTENSIONS_PORT_DVSEC_LENGTH,
EXTENSIONS_PORT_DVSEC,
EXTENSIONS_PORT_DVSEC_REVID, dvsec);
dvsec = (uint8_t *)&(CXLDVSECPortFlexBus){
.cap = 0x27, /* Cache, IO, Mem, non-MLD */
.ctrl = 0x27, /* Cache, IO, Mem */
- .status = 0x26, /* same */
+ .status = usp->flitmode ? 0x6 : 0x26, /* lack of 68B */
.rcvd_mod_ts_data_phase1 = 0xef, /* WTF? */
};
- cxl_component_create_dvsec(cxl, CXL2_UPSTREAM_PORT,
+ cxl_component_create_dvsec(cxl_cstate, CXL2_UPSTREAM_PORT,
PCIE_CXL3_FLEXBUS_PORT_DVSEC_LENGTH,
PCIE_FLEXBUS_PORT_DVSEC,
PCIE_CXL3_FLEXBUS_PORT_DVSEC_REVID, dvsec);
@@ -132,7 +133,7 @@ static void build_dvsecs(CXLComponentState *cxl)
.reg0_base_lo = RBI_COMPONENT_REG | CXL_COMPONENT_REG_BAR_IDX,
.reg0_base_hi = 0,
};
- cxl_component_create_dvsec(cxl, CXL2_UPSTREAM_PORT,
+ cxl_component_create_dvsec(cxl_cstate, CXL2_UPSTREAM_PORT,
REG_LOC_DVSEC_LENGTH, REG_LOC_DVSEC,
REG_LOC_DVSEC_REVID, dvsec);
}
@@ -327,7 +328,7 @@ static void cxl_usp_realize(PCIDevice *d, Error **errp)
}
cxl_cstate->dvsec_offset = CXL_UPSTREAM_PORT_DVSEC_OFFSET;
cxl_cstate->pdev = d;
- build_dvsecs(cxl_cstate);
+ build_dvsecs(usp);
cxl_component_register_block_init(OBJECT(d), cxl_cstate, TYPE_CXL_USP);
pci_register_bar(d, CXL_COMPONENT_REG_BAR_IDX,
PCI_BASE_ADDRESS_SPACE_MEMORY |
@@ -369,6 +370,7 @@ static const Property cxl_upstream_props[] = {
speed, PCIE_LINK_SPEED_32),
DEFINE_PROP_PCIE_LINK_WIDTH("x-width", CXLUpstreamPort,
width, PCIE_LINK_WIDTH_16),
+ DEFINE_PROP_BOOL("x-256b-flit", CXLUpstreamPort, flitmode, false),
};
static void cxl_upstream_class_init(ObjectClass *oc, const void *data)
diff --git a/hw/pci/pcie.c b/hw/pci/pcie.c
index c481c16c0f57..6cc6e848b6bf 100644
--- a/hw/pci/pcie.c
+++ b/hw/pci/pcie.c
@@ -113,7 +113,7 @@ pcie_cap_v1_fill(PCIDevice *dev, uint8_t port, uint8_t type, uint8_t version)
/* Includes setting the target speed default */
static void pcie_cap_fill_lnk(uint8_t *exp_cap, PCIExpLinkWidth width,
- PCIExpLinkSpeed speed)
+ PCIExpLinkSpeed speed, bool flitmode)
{
/* Clear and fill LNKCAP from what was configured above */
pci_long_test_and_clear_mask(exp_cap + PCI_EXP_LNKCAP,
@@ -158,10 +158,15 @@ static void pcie_cap_fill_lnk(uint8_t *exp_cap, PCIExpLinkWidth width,
PCI_EXP_LNKCAP2_SLS_64_0GB);
}
}
+
+ if (flitmode) {
+ pci_long_test_and_set_mask(exp_cap + PCI_EXP_LNKSTA2,
+ PCI_EXP_LNKSTA2_FLIT);
+ }
}
void pcie_cap_fill_link_ep_usp(PCIDevice *dev, PCIExpLinkWidth width,
- PCIExpLinkSpeed speed)
+ PCIExpLinkSpeed speed, bool flitmode)
{
uint8_t *exp_cap = dev->config + dev->exp.exp_cap;
@@ -175,7 +180,7 @@ void pcie_cap_fill_link_ep_usp(PCIDevice *dev, PCIExpLinkWidth width,
QEMU_PCI_EXP_LNKSTA_NLW(width) |
QEMU_PCI_EXP_LNKSTA_CLS(speed));
- pcie_cap_fill_lnk(exp_cap, width, speed);
+ pcie_cap_fill_lnk(exp_cap, width, speed, flitmode);
}
static void pcie_cap_fill_slot_lnk(PCIDevice *dev)
@@ -212,7 +217,7 @@ static void pcie_cap_fill_slot_lnk(PCIDevice *dev)
/* the PCI_EXP_LNKSTA_DLLLA will be set in the hotplug function */
}
- pcie_cap_fill_lnk(exp_cap, s->width, s->speed);
+ pcie_cap_fill_lnk(exp_cap, s->width, s->speed, s->flitmode);
}
int pcie_cap_init(PCIDevice *dev, uint8_t offset,
@@ -1175,6 +1180,8 @@ void pcie_sync_bridge_lnk(PCIDevice *bridge_dev)
if (!target || !target->exp.exp_cap) {
lnksta = lnkcap;
} else {
+ uint16_t lnksta2;
+
lnksta = target->config_read(target,
target->exp.exp_cap + PCI_EXP_LNKSTA,
sizeof(lnksta));
@@ -1188,6 +1195,14 @@ void pcie_sync_bridge_lnk(PCIDevice *bridge_dev)
lnksta &= ~PCI_EXP_LNKSTA_CLS;
lnksta |= lnkcap & PCI_EXP_LNKCAP_SLS;
}
+
+ lnksta2 = target->config_read(target,
+ target->exp.exp_cap + PCI_EXP_LNKSTA2,
+ sizeof(lnksta2));
+ pci_word_test_and_clear_mask(exp_cap + PCI_EXP_LNKSTA2,
+ PCI_EXP_LNKSTA2_FLIT);
+ pci_word_test_and_set_mask(exp_cap + PCI_EXP_LNKSTA2,
+ lnksta2 & PCI_EXP_LNKSTA2_FLIT);
}
if (!(lnksta & PCI_EXP_LNKSTA_NLW)) {
--
2.51.0
^ permalink raw reply related [flat|nested] 14+ messages in thread* [PATCH qemu v6 2/7] hw/cxl: Refactor component register initialization
2026-02-04 12:12 [PATCH qemu v6 0/7] hw/cxl: Support Back-Invalidate (+ PCIe Flit mode) Jonathan Cameron
2026-02-04 12:12 ` [PATCH qemu v6 1/7] hw/pcie: Support enabling flit mode Jonathan Cameron
@ 2026-02-04 12:12 ` Jonathan Cameron
2026-02-04 12:12 ` [PATCH qemu v6 3/7] tests/bios-tables-test: Excluded CEDT.cxl for BI restriction relaxation Jonathan Cameron
` (4 subsequent siblings)
6 siblings, 0 replies; 14+ messages in thread
From: Jonathan Cameron @ 2026-02-04 12:12 UTC (permalink / raw)
To: Michael Tsirkin, qemu-devel, Davidlohr Bueso
Cc: linuxarm, linux-cxl, Ravi Shankar, Marcel Apfelbaum,
Markus Armbruster, Michael Roth
From: Ira Weiny <ira.weiny@intel.com>
CXL 3.2 8.2.4 Table 8-22 defines which capabilities are mandatory, not
permitted, or optional for each type of device.
cxl_component_register_init_common() uses a rather odd 'fall through'
mechanism to define each component register set. This assumes that any
device or capability being added builds on the previous devices
capabilities. This is not true as there are mutually exclusive
capabilities defined. For example, downstream ports can not have snoop
but it can have Back Invalidate capable decoders.
Refactor this code to make it easier to add individual capabilities as
defined by a device type. Any capability which is not specified by the
type is left NULL'ed out which complies with the packed nature of the
register array.
Update all spec references to 3.2.
No functional changes should be seen with this patch.
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Tested-by: Dongjoo Seo <dongjoo.seo1@samsung.com>
[rebased, no RAS for HBs, r3.2 references]
Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
include/hw/cxl/cxl_component.h | 33 ++++++++++-----
hw/cxl/cxl-component-utils.c | 75 +++++++++++-----------------------
2 files changed, 46 insertions(+), 62 deletions(-)
diff --git a/include/hw/cxl/cxl_component.h b/include/hw/cxl/cxl_component.h
index b0f2aa791431..1f167d3ef79b 100644
--- a/include/hw/cxl/cxl_component.h
+++ b/include/hw/cxl/cxl_component.h
@@ -32,10 +32,20 @@ enum reg_type {
};
/*
- * Capability registers are defined at the top of the CXL.cache/mem region and
- * are packed. For our purposes we will always define the caps in the same
- * order.
- * CXL r3.1 Table 8-22: CXL_CAPABILITY_ID Assignment for details.
+ * CXL r3.2 - 8.2.4 Table 8-22 and 8-23
+ *
+ * Capability registers are defined at the top of the CXL.cache/mem region.
+ * They are defined to be packed and at variable offsets. However, NULL
+ * capabilities can be added to the packed array. To facilitate easier access
+ * within the QEMU code, define these at specified offsets. Then NULL out any
+ * capabilities for devices which don't (or can't) have a particular capability
+ * (see cxl_component_register_init_common). NULL capabilities are to be
+ * ignored by software.
+ *
+ * 'offsets' are based on index's which can then be used to report the array
+ * size in CXL Capability Header Register (index/offset 0).
+ *
+ * See CXL r3.2 Table 8-25 for an example of allowing a 'NULL' header.
*/
/* CXL r3.1 Section 8.2.4.1: CXL Capability Header Register */
@@ -46,16 +56,17 @@ REG32(CXL_CAPABILITY_HEADER, 0)
FIELD(CXL_CAPABILITY_HEADER, CACHE_MEM_VERSION, 20, 4)
FIELD(CXL_CAPABILITY_HEADER, ARRAY_SIZE, 24, 8)
-#define CXLx_CAPABILITY_HEADER(type, offset) \
- REG32(CXL_##type##_CAPABILITY_HEADER, offset) \
+#define CXLx_CAPABILITY_HEADER(type, idx) \
+ enum { CXL_##type##_CAP_HDR_IDX = idx }; \
+ REG32(CXL_##type##_CAPABILITY_HEADER, (idx * 0x4)) \
FIELD(CXL_##type##_CAPABILITY_HEADER, ID, 0, 16) \
FIELD(CXL_##type##_CAPABILITY_HEADER, VERSION, 16, 4) \
FIELD(CXL_##type##_CAPABILITY_HEADER, PTR, 20, 12)
-CXLx_CAPABILITY_HEADER(RAS, 0x4)
-CXLx_CAPABILITY_HEADER(LINK, 0x8)
-CXLx_CAPABILITY_HEADER(HDM, 0xc)
-CXLx_CAPABILITY_HEADER(EXTSEC, 0x10)
-CXLx_CAPABILITY_HEADER(SNOOP, 0x14)
+CXLx_CAPABILITY_HEADER(RAS, 1)
+CXLx_CAPABILITY_HEADER(LINK, 2)
+CXLx_CAPABILITY_HEADER(HDM, 3)
+CXLx_CAPABILITY_HEADER(EXTSEC, 4)
+CXLx_CAPABILITY_HEADER(SNOOP, 5)
/*
* Capability structures contain the actual registers that the CXL component
diff --git a/hw/cxl/cxl-component-utils.c b/hw/cxl/cxl-component-utils.c
index 473895948b3d..91770f103a85 100644
--- a/hw/cxl/cxl-component-utils.c
+++ b/hw/cxl/cxl-component-utils.c
@@ -284,32 +284,6 @@ void cxl_component_register_init_common(uint32_t *reg_state,
{
int caps = 0;
- /*
- * In CXL 2.0 the capabilities required for each CXL component are such
- * that, with the ordering chosen here, a single number can be used to
- * define which capabilities should be provided.
- */
- switch (type) {
- case CXL2_DOWNSTREAM_PORT:
- case CXL2_DEVICE:
- /* RAS, Link */
- caps = 2;
- break;
- case CXL2_UPSTREAM_PORT:
- case CXL2_TYPE3_DEVICE:
- case CXL2_LOGICAL_DEVICE:
- /* + HDM */
- caps = 3;
- break;
- case CXL2_ROOT_PORT:
- case CXL2_RC:
- /* + Extended Security, + Snoop */
- caps = 5;
- break;
- default:
- abort();
- }
-
memset(reg_state, 0, CXL2_COMPONENT_CM_REGION_SIZE);
/* CXL Capability Header Register */
@@ -317,11 +291,12 @@ void cxl_component_register_init_common(uint32_t *reg_state,
ARRAY_FIELD_DP32(reg_state, CXL_CAPABILITY_HEADER, VERSION,
CXL_CAPABILITY_VERSION);
ARRAY_FIELD_DP32(reg_state, CXL_CAPABILITY_HEADER, CACHE_MEM_VERSION, 1);
- ARRAY_FIELD_DP32(reg_state, CXL_CAPABILITY_HEADER, ARRAY_SIZE, caps);
#define init_cap_reg(reg, id, version) \
do { \
- int which = R_CXL_##reg##_CAPABILITY_HEADER; \
+ int which = CXL_##reg##_CAP_HDR_IDX; \
+ if (CXL_##reg##_CAP_HDR_IDX > caps) \
+ caps = CXL_##reg##_CAP_HDR_IDX; \
reg_state[which] = FIELD_DP32(reg_state[which], \
CXL_##reg##_CAPABILITY_HEADER, ID, id); \
reg_state[which] = \
@@ -332,37 +307,35 @@ void cxl_component_register_init_common(uint32_t *reg_state,
CXL_##reg##_REGISTERS_OFFSET); \
} while (0)
+ /* CXL r3.2 8.2.4 Table 8-22 */
switch (type) {
- case CXL2_DEVICE:
- case CXL2_TYPE3_DEVICE:
- case CXL2_LOGICAL_DEVICE:
case CXL2_ROOT_PORT:
+ case CXL2_RC:
+ /* + Extended Security, + Snoop */
+ init_cap_reg(EXTSEC, 6, 1);
+ init_cap_reg(SNOOP, 8, 1);
+ /* fallthrough */
case CXL2_UPSTREAM_PORT:
+ case CXL2_TYPE3_DEVICE:
+ case CXL2_LOGICAL_DEVICE:
+ /* + HDM */
+ init_cap_reg(HDM, 5, 1);
+ hdm_init_common(reg_state, write_msk, type);
+ /* fallthrough */
case CXL2_DOWNSTREAM_PORT:
- init_cap_reg(RAS, 2, CXL_RAS_CAPABILITY_VERSION);
- ras_init_common(reg_state, write_msk);
+ case CXL2_DEVICE:
+ /* RAS, Link */
+ if (type != CXL2_RC) {
+ init_cap_reg(RAS, 2, 2);
+ ras_init_common(reg_state, write_msk);
+ }
+ init_cap_reg(LINK, 4, 2);
break;
default:
- break;
- }
-
- init_cap_reg(LINK, 4, CXL_LINK_CAPABILITY_VERSION);
-
- if (caps < 3) {
- return;
- }
-
- if (type != CXL2_ROOT_PORT) {
- init_cap_reg(HDM, 5, CXL_HDM_CAPABILITY_VERSION);
- hdm_init_common(reg_state, write_msk, type);
- }
- if (caps < 5) {
- return;
+ abort();
}
- init_cap_reg(EXTSEC, 6, CXL_EXTSEC_CAP_VERSION);
- init_cap_reg(SNOOP, 8, CXL_SNOOP_CAP_VERSION);
-
+ ARRAY_FIELD_DP32(reg_state, CXL_CAPABILITY_HEADER, ARRAY_SIZE, caps);
#undef init_cap_reg
}
--
2.51.0
^ permalink raw reply related [flat|nested] 14+ messages in thread* [PATCH qemu v6 3/7] tests/bios-tables-test: Excluded CEDT.cxl for BI restriction relaxation.
2026-02-04 12:12 [PATCH qemu v6 0/7] hw/cxl: Support Back-Invalidate (+ PCIe Flit mode) Jonathan Cameron
2026-02-04 12:12 ` [PATCH qemu v6 1/7] hw/pcie: Support enabling flit mode Jonathan Cameron
2026-02-04 12:12 ` [PATCH qemu v6 2/7] hw/cxl: Refactor component register initialization Jonathan Cameron
@ 2026-02-04 12:12 ` Jonathan Cameron
2026-02-04 12:12 ` [PATCH qemu v6 4/7] hw/cxl: Update CXL Fixed Memory Window ACPI description to include Back Invalidate support Jonathan Cameron
` (3 subsequent siblings)
6 siblings, 0 replies; 14+ messages in thread
From: Jonathan Cameron @ 2026-02-04 12:12 UTC (permalink / raw)
To: Michael Tsirkin, qemu-devel, Davidlohr Bueso
Cc: linuxarm, linux-cxl, Ravi Shankar, Marcel Apfelbaum,
Markus Armbruster, Michael Roth
The next patch will relax restrictions on the fixed memory window
to allow use with back invalidate capable devices.
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
tests/qtest/bios-tables-test-allowed-diff.h | 1 +
1 file changed, 1 insertion(+)
diff --git a/tests/qtest/bios-tables-test-allowed-diff.h b/tests/qtest/bios-tables-test-allowed-diff.h
index dfb8523c8bf4..b4646b5b3147 100644
--- a/tests/qtest/bios-tables-test-allowed-diff.h
+++ b/tests/qtest/bios-tables-test-allowed-diff.h
@@ -1 +1,2 @@
/* List of comma-separated changed AML files to ignore */
+"tests/data/acpi/x86/q35/CEDT.cxl",
--
2.51.0
^ permalink raw reply related [flat|nested] 14+ messages in thread* [PATCH qemu v6 4/7] hw/cxl: Update CXL Fixed Memory Window ACPI description to include Back Invalidate support.
2026-02-04 12:12 [PATCH qemu v6 0/7] hw/cxl: Support Back-Invalidate (+ PCIe Flit mode) Jonathan Cameron
` (2 preceding siblings ...)
2026-02-04 12:12 ` [PATCH qemu v6 3/7] tests/bios-tables-test: Excluded CEDT.cxl for BI restriction relaxation Jonathan Cameron
@ 2026-02-04 12:12 ` Jonathan Cameron
2026-02-04 12:12 ` [PATCH qemu v6 5/7] tests/acpi/cxl: Update CEDT.cxl to allow BI in CFWMS Jonathan Cameron
` (2 subsequent siblings)
6 siblings, 0 replies; 14+ messages in thread
From: Jonathan Cameron @ 2026-02-04 12:12 UTC (permalink / raw)
To: Michael Tsirkin, qemu-devel, Davidlohr Bueso
Cc: linuxarm, linux-cxl, Ravi Shankar, Marcel Apfelbaum,
Markus Armbruster, Michael Roth
Defaults for these windows has always been to enable anything QEMU supports.
With the addition of back invalidate support it is necessary to specify that
host windows support this.
CXL emulation is currently only suitable for software stack verification.
The relaxation of the restrictions on this window to include BI have no
affect on the OS until BI capable devices are added and until now these
have not existed. As such no backwards compatibility impacts are expected
from this change.
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
hw/acpi/cxl.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/hw/acpi/cxl.c b/hw/acpi/cxl.c
index 75edb2c0a652..f92f7fa3d558 100644
--- a/hw/acpi/cxl.c
+++ b/hw/acpi/cxl.c
@@ -172,7 +172,7 @@ static void cedt_build_cfmws(CXLFixedWindow *fw, Aml *cedt)
build_append_int_noprefix(table_data, fw->enc_int_gran, 4);
/* Window Restrictions */
- build_append_int_noprefix(table_data, 0x0f, 2);
+ build_append_int_noprefix(table_data, 0x2f, 2);
/* QTG ID */
build_append_int_noprefix(table_data, 0, 2);
--
2.51.0
^ permalink raw reply related [flat|nested] 14+ messages in thread* [PATCH qemu v6 5/7] tests/acpi/cxl: Update CEDT.cxl to allow BI in CFWMS
2026-02-04 12:12 [PATCH qemu v6 0/7] hw/cxl: Support Back-Invalidate (+ PCIe Flit mode) Jonathan Cameron
` (3 preceding siblings ...)
2026-02-04 12:12 ` [PATCH qemu v6 4/7] hw/cxl: Update CXL Fixed Memory Window ACPI description to include Back Invalidate support Jonathan Cameron
@ 2026-02-04 12:12 ` Jonathan Cameron
2026-02-04 12:12 ` [PATCH qemu v6 6/7] hw/cxl: Support type3 HDM-DB Jonathan Cameron
2026-02-04 12:12 ` [PATCH qemu v6 7/7] hw/cxl: Remove register special_ops->read() Jonathan Cameron
6 siblings, 0 replies; 14+ messages in thread
From: Jonathan Cameron @ 2026-02-04 12:12 UTC (permalink / raw)
To: Michael Tsirkin, qemu-devel, Davidlohr Bueso
Cc: linuxarm, linux-cxl, Ravi Shankar, Marcel Apfelbaum,
Markus Armbruster, Michael Roth
With the addition of back invalidate support in the CXL emulation relax
the restriction on the CXL Fixed Memory Window Structures so all
advertised ranges continue to support being used with all features that
QEMU emulates.
[064h 0100 001h] Subtable Type : 01 [CXL Fixed Memory Window Structure]
[065h 0101 001h] Reserved : 00
[066h 0102 002h] Length : 0028
[068h 0104 004h] Reserved : 00000000
[06Ch 0108 008h] Window base address : 0000000110000000
[074h 0116 008h] Window size : 0000000100000000
[07Ch 0124 001h] Interleave Members : 00
[07Dh 0125 001h] Interleave Arithmetic : 00
[07Eh 0126 002h] Reserved : 0000
[080h 0128 004h] Granularity : 00000005
[084h 0132 002h] Restrictions : 002F # Changed from 000F
[086h 0134 002h] QtgId : 0000
[088h 0136 004h] First Target : 0000000C
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
tests/qtest/bios-tables-test-allowed-diff.h | 1 -
tests/data/acpi/x86/q35/CEDT.cxl | Bin 184 -> 184 bytes
2 files changed, 1 deletion(-)
diff --git a/tests/qtest/bios-tables-test-allowed-diff.h b/tests/qtest/bios-tables-test-allowed-diff.h
index b4646b5b3147..dfb8523c8bf4 100644
--- a/tests/qtest/bios-tables-test-allowed-diff.h
+++ b/tests/qtest/bios-tables-test-allowed-diff.h
@@ -1,2 +1 @@
/* List of comma-separated changed AML files to ignore */
-"tests/data/acpi/x86/q35/CEDT.cxl",
diff --git a/tests/data/acpi/x86/q35/CEDT.cxl b/tests/data/acpi/x86/q35/CEDT.cxl
index ff8203af070241bd23dd0eb8a51460692bb7d229..c35f3882eee67aa5613af427234d1ccd196aa249 100644
GIT binary patch
delta 36
ncmdnNxPy_)+0`Xv2Ll5G<Hm_xRgC%*Th)2=fm|LSz6Znrs#OQB
delta 36
ncmdnNxPy_)+0`Xv2Ll5G<Hw0yRgC--Th)2^fm|LSz6ZnrtThL&
--
2.51.0
^ permalink raw reply related [flat|nested] 14+ messages in thread* [PATCH qemu v6 6/7] hw/cxl: Support type3 HDM-DB
2026-02-04 12:12 [PATCH qemu v6 0/7] hw/cxl: Support Back-Invalidate (+ PCIe Flit mode) Jonathan Cameron
` (4 preceding siblings ...)
2026-02-04 12:12 ` [PATCH qemu v6 5/7] tests/acpi/cxl: Update CEDT.cxl to allow BI in CFWMS Jonathan Cameron
@ 2026-02-04 12:12 ` Jonathan Cameron
2026-02-04 13:24 ` Michael S. Tsirkin
2026-02-04 12:12 ` [PATCH qemu v6 7/7] hw/cxl: Remove register special_ops->read() Jonathan Cameron
6 siblings, 1 reply; 14+ messages in thread
From: Jonathan Cameron @ 2026-02-04 12:12 UTC (permalink / raw)
To: Michael Tsirkin, qemu-devel, Davidlohr Bueso
Cc: linuxarm, linux-cxl, Ravi Shankar, Marcel Apfelbaum,
Markus Armbruster, Michael Roth
From: Davidlohr Bueso <dave@stgolabs.net>
Add basic plumbing for memory expander devices that support Back
Invalidation. This introduces a 'hdm-db=on|off' parameter and
exposes the relevant BI RT/Decoder component cachemem registers.
Some noteworthy properties:
- Devices require enabling Flit mode across the CXL topology.
- Explicit BI-ID commit is required.
- HDM decoder support both host and dev coherency models.
Tested-by: Dongjoo Seo <dongjoo.seo1@samsung.com>
Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
v6: Initialize type variable to avoid a false compiler warning
from some versions of gcc. (Michael Tsirkin)
---
docs/system/devices/cxl.rst | 23 +++++
include/hw/cxl/cxl_component.h | 54 ++++++++++-
include/hw/cxl/cxl_device.h | 3 +
hw/cxl/cxl-component-utils.c | 142 ++++++++++++++++++++++++++--
hw/mem/cxl_type3.c | 9 +-
hw/pci-bridge/cxl_downstream.c | 2 +-
hw/pci-bridge/cxl_root_port.c | 3 +-
hw/pci-bridge/cxl_upstream.c | 2 +-
hw/pci-bridge/pci_expander_bridge.c | 2 +-
9 files changed, 225 insertions(+), 15 deletions(-)
diff --git a/docs/system/devices/cxl.rst b/docs/system/devices/cxl.rst
index ca15a0da1c1d..9d0771cdfd73 100644
--- a/docs/system/devices/cxl.rst
+++ b/docs/system/devices/cxl.rst
@@ -384,6 +384,29 @@ An example of 4 devices below a switch suitable for 1, 2 or 4 way interleave::
-device cxl-type3,bus=swport3,persistent-memdev=cxl-mem3,lsa=cxl-lsa3,id=cxl-pmem3,sn=0x4 \
-M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
+An example of 4 type3 devices with volatile memory below a switch. Two of the devices
+use HDM-DB for coherence, which requires operating in Flit mode::
+
+ qemu-system-x86_64 -M q35,cxl=on -m 4G,maxmem=8G,slots=8 -smp 4 \
+ ...
+ -object memory-backend-ram,id=cxl-mem0,share=on,size=256M \
+ -object memory-backend-ram,id=cxl-mem1,share=on,size=256M \
+ -object memory-backend-ram,id=cxl-mem2,share=on,size=256M \
+ -object memory-backend-ram,id=cxl-mem3,share=on,size=256M \
+ -device pxb-cxl,bus_nr=12,bus=pcie.0,id=cxl.1 \
+ -device cxl-rp,port=0,bus=cxl.1,id=root_port0,chassis=0,slot=0 \
+ -device cxl-rp,port=1,bus=cxl.1,id=root_port1,chassis=0,slot=1 \
+ -device cxl-upstream,bus=root_port0,id=us0,x-256b-flit=on \
+ -device cxl-downstream,port=0,bus=us0,id=swport0,chassis=0,slot=4 \
+ -device cxl-type3,bus=swport0,volatile-memdev=cxl-mem0,id=cxl-mem0,sn=0x1,x-256b-flit=on,hdm-db=on \
+ -device cxl-downstream,port=1,bus=us0,id=swport1,chassis=0,slot=5 \
+ -device cxl-type3,bus=swport1,volatile-memdev=cxl-mem1,id=cxl-mem1,sn=0x2,x-256b-flit=on,hdm-db=on \
+ -device cxl-downstream,port=2,bus=us0,id=swport2,chassis=0,slot=6 \
+ -device cxl-type3,bus=swport2,volatile-memdev=cxl-mem2,id=cxl-mem2,sn=0x3 \
+ -device cxl-downstream,port=3,bus=us0,id=swport3,chassis=0,slot=7 \
+ -device cxl-type3,bus=swport3,volatile-memdev=cxl-mem3,id=cxl-mem3,sn=0x4 \
+ -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
+
A simple arm/virt example featuring a single direct connected CXL Type 3
Volatile Memory device::
diff --git a/include/hw/cxl/cxl_component.h b/include/hw/cxl/cxl_component.h
index 1f167d3ef79b..ffc82202206c 100644
--- a/include/hw/cxl/cxl_component.h
+++ b/include/hw/cxl/cxl_component.h
@@ -67,6 +67,8 @@ CXLx_CAPABILITY_HEADER(LINK, 2)
CXLx_CAPABILITY_HEADER(HDM, 3)
CXLx_CAPABILITY_HEADER(EXTSEC, 4)
CXLx_CAPABILITY_HEADER(SNOOP, 5)
+CXLx_CAPABILITY_HEADER(BI_RT, 6)
+CXLx_CAPABILITY_HEADER(BI_DECODER, 7)
/*
* Capability structures contain the actual registers that the CXL component
@@ -211,10 +213,55 @@ HDM_DECODER_INIT(3);
(CXL_IDE_REGISTERS_OFFSET + CXL_IDE_REGISTERS_SIZE)
#define CXL_SNOOP_REGISTERS_SIZE 0x8
-QEMU_BUILD_BUG_MSG((CXL_SNOOP_REGISTERS_OFFSET +
- CXL_SNOOP_REGISTERS_SIZE) >= 0x1000,
+#define CXL_BI_RT_CAP_VERSION 1
+#define CXL_BI_RT_REGISTERS_OFFSET \
+ (CXL_SNOOP_REGISTERS_OFFSET + CXL_SNOOP_REGISTERS_SIZE)
+#define CXL_BI_RT_REGISTERS_SIZE 0xC
+
+REG32(CXL_BI_RT_CAPABILITY, CXL_BI_RT_REGISTERS_OFFSET)
+ FIELD(CXL_BI_RT_CAPABILITY, EXPLICIT_COMMIT, 0, 1)
+REG32(CXL_BI_RT_CTRL, CXL_BI_RT_REGISTERS_OFFSET + 0x4)
+ FIELD(CXL_BI_RT_CTRL, COMMIT, 0, 1)
+REG32(CXL_BI_RT_STATUS, CXL_BI_RT_REGISTERS_OFFSET + 0x8)
+ FIELD(CXL_BI_RT_STATUS, COMMITTED, 0, 1)
+ FIELD(CXL_BI_RT_STATUS, ERR_NOT_COMMITTED, 1, 1)
+ FIELD(CXL_BI_RT_STATUS, COMMIT_TMO_SCALE, 8, 4)
+ FIELD(CXL_BI_RT_STATUS, COMMIT_TMO_BASE, 12, 4)
+
+/* CXL r3.2 8.2.4.27 - CXL BI Decoder Capability Structure */
+#define CXL_BI_DECODER_CAP_VERSION 1
+#define CXL_BI_DECODER_REGISTERS_OFFSET \
+ (CXL_BI_RT_REGISTERS_OFFSET + CXL_BI_RT_REGISTERS_SIZE)
+#define CXL_BI_DECODER_REGISTERS_SIZE 0xC
+
+REG32(CXL_BI_DECODER_CAPABILITY, CXL_BI_DECODER_REGISTERS_OFFSET)
+ FIELD(CXL_BI_DECODER_CAPABILITY, HDM_D, 0, 1)
+ FIELD(CXL_BI_DECODER_CAPABILITY, EXPLICIT_COMMIT, 1, 1)
+REG32(CXL_BI_DECODER_CTRL, CXL_BI_DECODER_REGISTERS_OFFSET + 0x4)
+ FIELD(CXL_BI_DECODER_CTRL, BI_FW, 0, 1)
+ FIELD(CXL_BI_DECODER_CTRL, BI_ENABLE, 1, 1)
+ FIELD(CXL_BI_DECODER_CTRL, COMMIT, 2, 1)
+REG32(CXL_BI_DECODER_STATUS, CXL_BI_DECODER_REGISTERS_OFFSET + 0x8)
+ FIELD(CXL_BI_DECODER_STATUS, COMMITTED, 0, 1)
+ FIELD(CXL_BI_DECODER_STATUS, ERR_NOT_COMMITTED, 1, 1)
+ FIELD(CXL_BI_DECODER_STATUS, COMMIT_TMO_SCALE, 8, 4)
+ FIELD(CXL_BI_DECODER_STATUS, COMMIT_TMO_BASE, 12, 4)
+
+QEMU_BUILD_BUG_MSG((CXL_BI_DECODER_REGISTERS_OFFSET +
+ CXL_BI_DECODER_REGISTERS_SIZE) >= 0x1000,
"No space for registers");
+/* track BI explicit commit handling for route table and decoder */
+enum {
+ CXL_BISTATE_RT = 0,
+ CXL_BISTATE_DECODER,
+ CXL_BISTATE_MAX
+};
+
+typedef struct bi_state {
+ uint64_t last_commit; /* last 0->1 transition */
+} BIState;
+
typedef struct component_registers {
/*
* Main memory region to be registered with QEMU core.
@@ -259,6 +306,7 @@ typedef struct cxl_component {
};
CDATObject cdat;
+ BIState bi_state[CXL_BISTATE_MAX];
} CXLComponentState;
void cxl_component_register_block_init(Object *obj,
@@ -266,7 +314,7 @@ void cxl_component_register_block_init(Object *obj,
const char *type);
void cxl_component_register_init_common(uint32_t *reg_state,
uint32_t *write_msk,
- enum reg_type type);
+ enum reg_type type, bool bi);
void cxl_component_create_dvsec(CXLComponentState *cxl_cstate,
enum reg_type cxl_dev_type, uint16_t length,
diff --git a/include/hw/cxl/cxl_device.h b/include/hw/cxl/cxl_device.h
index 7d9236db8c85..393f3122173b 100644
--- a/include/hw/cxl/cxl_device.h
+++ b/include/hw/cxl/cxl_device.h
@@ -770,6 +770,9 @@ struct CXLType3Dev {
CXLMemSparingReadAttrs rank_sparing_attrs;
CXLMemSparingWriteAttrs rank_sparing_wr_attrs;
+ /* BI flows */
+ bool hdmdb;
+
struct dynamic_capacity {
HostMemoryBackend *host_dc;
AddressSpace host_dc_as;
diff --git a/hw/cxl/cxl-component-utils.c b/hw/cxl/cxl-component-utils.c
index 91770f103a85..a7d36e1128c2 100644
--- a/hw/cxl/cxl-component-utils.c
+++ b/hw/cxl/cxl-component-utils.c
@@ -71,10 +71,40 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
case 4:
if (cregs->special_ops && cregs->special_ops->read) {
return cregs->special_ops->read(cxl_cstate, offset, 4);
- } else {
- QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
- return cregs->cache_mem_registers[offset / 4];
}
+
+ QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
+
+ if (offset == A_CXL_BI_RT_STATUS ||
+ offset == A_CXL_BI_DECODER_STATUS) {
+ int type;
+ uint64_t started;
+
+ type = (offset == A_CXL_BI_RT_STATUS) ?
+ CXL_BISTATE_RT : CXL_BISTATE_DECODER;
+ started = cxl_cstate->bi_state[type].last_commit;
+
+ if (started) {
+ uint32_t *cache_mem = cregs->cache_mem_registers;
+ uint32_t val = cache_mem[offset / 4];
+ uint64_t now;
+ int set;
+
+ now = qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
+ /* arbitrary 100 ms to do the commit */
+ set = !!(now >= started + 100);
+
+ if (offset == A_CXL_BI_RT_STATUS) {
+ val = FIELD_DP32(val, CXL_BI_RT_STATUS, COMMITTED, set);
+ } else {
+ val = FIELD_DP32(val, CXL_BI_DECODER_STATUS, COMMITTED,
+ set);
+ }
+ stl_le_p((uint8_t *)cache_mem + offset, val);
+ }
+ }
+
+ return cregs->cache_mem_registers[offset / 4];
case 8:
qemu_log_mask(LOG_UNIMP,
"CXL 8 byte cache mem registers not implemented\n");
@@ -118,6 +148,47 @@ static void dumb_hdm_handler(CXLComponentState *cxl_cstate, hwaddr offset,
stl_le_p((uint8_t *)cache_mem + offset, value);
}
+static void bi_handler(CXLComponentState *cxl_cstate, hwaddr offset,
+ uint32_t value)
+{
+ ComponentRegisters *cregs = &cxl_cstate->crb;
+ uint32_t sts, *cache_mem = cregs->cache_mem_registers;
+ bool to_commit = false;
+ int type = 0; /* Unused value - work around for compiler warning */
+
+ switch (offset) {
+ case A_CXL_BI_RT_CTRL:
+ to_commit = FIELD_EX32(value, CXL_BI_RT_CTRL, COMMIT);
+ if (to_commit) {
+ sts = cxl_cache_mem_read_reg(cxl_cstate,
+ R_CXL_BI_RT_STATUS, 4);
+ sts = FIELD_DP32(sts, CXL_BI_RT_STATUS, COMMITTED, 0);
+ stl_le_p((uint8_t *)cache_mem + R_CXL_BI_RT_STATUS, sts);
+ type = CXL_BISTATE_RT;
+ }
+ break;
+ case A_CXL_BI_DECODER_CTRL:
+ to_commit = FIELD_EX32(value, CXL_BI_DECODER_CTRL, COMMIT);
+ if (to_commit) {
+ sts = cxl_cache_mem_read_reg(cxl_cstate,
+ R_CXL_BI_DECODER_STATUS, 4);
+ sts = FIELD_DP32(sts, CXL_BI_DECODER_STATUS, COMMITTED, 0);
+ stl_le_p((uint8_t *)cache_mem + R_CXL_BI_DECODER_STATUS, sts);
+ type = CXL_BISTATE_DECODER;
+ }
+ break;
+ default:
+ break;
+ }
+
+ if (to_commit) {
+ cxl_cstate->bi_state[type].last_commit =
+ qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
+ }
+
+ stl_le_p((uint8_t *)cache_mem + offset, value);
+}
+
static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
unsigned size)
{
@@ -141,6 +212,9 @@ static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
if (offset >= A_CXL_HDM_DECODER_CAPABILITY &&
offset <= A_CXL_HDM_DECODER3_TARGET_LIST_HI) {
dumb_hdm_handler(cxl_cstate, offset, value);
+ } else if (offset == A_CXL_BI_RT_CTRL ||
+ offset == A_CXL_BI_DECODER_CTRL) {
+ bi_handler(cxl_cstate, offset, value);
} else {
cregs->cache_mem_registers[offset / 4] = value;
}
@@ -230,7 +304,7 @@ static void ras_init_common(uint32_t *reg_state, uint32_t *write_msk)
}
static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
- enum reg_type type)
+ enum reg_type type, bool bi)
{
int decoder_count = CXL_HDM_DECODER_COUNT;
int hdm_inc = R_CXL_HDM_DECODER1_BASE_LO - R_CXL_HDM_DECODER0_BASE_LO;
@@ -255,7 +329,9 @@ static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
UIO_DECODER_COUNT, 0);
ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, MEMDATA_NXM_CAP, 0);
ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY,
- SUPPORTED_COHERENCY_MODEL, 0); /* Unknown */
+ SUPPORTED_COHERENCY_MODEL,
+ /* host+dev or Unknown */
+ type == CXL2_TYPE3_DEVICE && bi ? 3 : 0);
ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_GLOBAL_CONTROL,
HDM_DECODER_ENABLE, 0);
write_msk[R_CXL_HDM_DECODER_GLOBAL_CONTROL] = 0x3;
@@ -278,9 +354,43 @@ static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
}
}
+static void bi_rt_init_common(uint32_t *reg_state, uint32_t *write_msk)
+{
+ /* switch usp must commit the new BI-ID, timeout of 2secs */
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_CAPABILITY, EXPLICIT_COMMIT, 1);
+
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_CTRL, COMMIT, 0);
+ write_msk[R_CXL_BI_RT_CTRL] = 0x1;
+
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMITTED, 0);
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, ERR_NOT_COMMITTED, 0);
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMIT_TMO_SCALE, 0x6);
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMIT_TMO_BASE, 0x2);
+}
+
+static void bi_decoder_init_common(uint32_t *reg_state, uint32_t *write_msk,
+ enum reg_type type)
+{
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CAPABILITY, HDM_D, 0);
+ /* switch dsp must commit the new BI-ID, timeout of 2secs */
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CAPABILITY, EXPLICIT_COMMIT,
+ (type != CXL2_ROOT_PORT && type != CXL2_TYPE3_DEVICE));
+
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, BI_FW, 0);
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, BI_ENABLE, 0);
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, COMMIT, 0);
+ write_msk[R_CXL_BI_DECODER_CTRL] = 0x7;
+
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMITTED, 0);
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, ERR_NOT_COMMITTED, 0);
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMIT_TMO_SCALE, 0x6);
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMIT_TMO_BASE, 0x2);
+}
+
void cxl_component_register_init_common(uint32_t *reg_state,
uint32_t *write_msk,
- enum reg_type type)
+ enum reg_type type,
+ bool bi)
{
int caps = 0;
@@ -320,7 +430,7 @@ void cxl_component_register_init_common(uint32_t *reg_state,
case CXL2_LOGICAL_DEVICE:
/* + HDM */
init_cap_reg(HDM, 5, 1);
- hdm_init_common(reg_state, write_msk, type);
+ hdm_init_common(reg_state, write_msk, type, bi);
/* fallthrough */
case CXL2_DOWNSTREAM_PORT:
case CXL2_DEVICE:
@@ -335,6 +445,24 @@ void cxl_component_register_init_common(uint32_t *reg_state,
abort();
}
+ /* back invalidate */
+ if (bi) {
+ switch (type) {
+ case CXL2_UPSTREAM_PORT:
+ init_cap_reg(BI_RT, 11, CXL_BI_RT_CAP_VERSION);
+ bi_rt_init_common(reg_state, write_msk);
+ break;
+ case CXL2_ROOT_PORT:
+ case CXL2_DOWNSTREAM_PORT:
+ case CXL2_TYPE3_DEVICE:
+ init_cap_reg(BI_DECODER, 12, CXL_BI_DECODER_CAP_VERSION);
+ bi_decoder_init_common(reg_state, write_msk, type);
+ break;
+ default:
+ break;
+ }
+ }
+
ARRAY_FIELD_DP32(reg_state, CXL_CAPABILITY_HEADER, ARRAY_SIZE, caps);
#undef init_cap_reg
}
diff --git a/hw/mem/cxl_type3.c b/hw/mem/cxl_type3.c
index 3c7ecd8c48bc..3f09c589ae58 100644
--- a/hw/mem/cxl_type3.c
+++ b/hw/mem/cxl_type3.c
@@ -748,6 +748,11 @@ static bool cxl_setup_memory(CXLType3Dev *ct3d, Error **errp)
return false;
}
+ if (!ct3d->flitmode && ct3d->hdmdb) {
+ error_setg(errp, "hdm-db requires operating in 256b flit");
+ return false;
+ }
+
if (ct3d->hostvmem) {
MemoryRegion *vmr;
char *v_name;
@@ -1317,7 +1322,8 @@ static void ct3d_reset(DeviceState *dev)
pcie_cap_fill_link_ep_usp(PCI_DEVICE(dev), ct3d->width, ct3d->speed,
ct3d->flitmode);
- cxl_component_register_init_common(reg_state, write_msk, CXL2_TYPE3_DEVICE);
+ cxl_component_register_init_common(reg_state, write_msk,
+ CXL2_TYPE3_DEVICE, ct3d->hdmdb);
cxl_device_register_init_t3(ct3d, CXL_T3_MSIX_MBOX);
/*
@@ -1356,6 +1362,7 @@ static const Property ct3_props[] = {
DEFINE_PROP_PCIE_LINK_WIDTH("x-width", CXLType3Dev,
width, PCIE_LINK_WIDTH_16),
DEFINE_PROP_BOOL("x-256b-flit", CXLType3Dev, flitmode, false),
+ DEFINE_PROP_BOOL("hdm-db", CXLType3Dev, hdmdb, false),
};
static uint64_t get_lsa_size(CXLType3Dev *ct3d)
diff --git a/hw/pci-bridge/cxl_downstream.c b/hw/pci-bridge/cxl_downstream.c
index 64086d8ec2f2..320818a8f1ce 100644
--- a/hw/pci-bridge/cxl_downstream.c
+++ b/hw/pci-bridge/cxl_downstream.c
@@ -39,7 +39,7 @@ static void latch_registers(CXLDownstreamPort *dsp)
uint32_t *write_msk = dsp->cxl_cstate.crb.cache_mem_regs_write_mask;
cxl_component_register_init_common(reg_state, write_msk,
- CXL2_DOWNSTREAM_PORT);
+ CXL2_DOWNSTREAM_PORT, true);
}
/* TODO: Look at sharing this code across all CXL port types */
diff --git a/hw/pci-bridge/cxl_root_port.c b/hw/pci-bridge/cxl_root_port.c
index 5641048084a4..e2093ac39ee6 100644
--- a/hw/pci-bridge/cxl_root_port.c
+++ b/hw/pci-bridge/cxl_root_port.c
@@ -101,7 +101,8 @@ static void latch_registers(CXLRootPort *crp)
uint32_t *reg_state = crp->cxl_cstate.crb.cache_mem_registers;
uint32_t *write_msk = crp->cxl_cstate.crb.cache_mem_regs_write_mask;
- cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT);
+ cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT,
+ true);
}
static void build_dvsecs(PCIDevice *d, CXLComponentState *cxl)
diff --git a/hw/pci-bridge/cxl_upstream.c b/hw/pci-bridge/cxl_upstream.c
index c352d11dc7b7..fb8d19539c9f 100644
--- a/hw/pci-bridge/cxl_upstream.c
+++ b/hw/pci-bridge/cxl_upstream.c
@@ -90,7 +90,7 @@ static void latch_registers(CXLUpstreamPort *usp)
uint32_t *write_msk = usp->cxl_cstate.crb.cache_mem_regs_write_mask;
cxl_component_register_init_common(reg_state, write_msk,
- CXL2_UPSTREAM_PORT);
+ CXL2_UPSTREAM_PORT, usp->flitmode);
ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, TARGET_COUNT, 8);
}
diff --git a/hw/pci-bridge/pci_expander_bridge.c b/hw/pci-bridge/pci_expander_bridge.c
index b6e2eb796951..11623a5666f6 100644
--- a/hw/pci-bridge/pci_expander_bridge.c
+++ b/hw/pci-bridge/pci_expander_bridge.c
@@ -300,7 +300,7 @@ static void pxb_cxl_dev_reset(DeviceState *dev)
uint32_t *write_msk = cxl_cstate->crb.cache_mem_regs_write_mask;
int dsp_count = 0;
- cxl_component_register_init_common(reg_state, write_msk, CXL2_RC);
+ cxl_component_register_init_common(reg_state, write_msk, CXL2_RC, false);
/*
* The CXL specification allows for host bridges with no HDM decoders
* if they only have a single root port.
--
2.51.0
^ permalink raw reply related [flat|nested] 14+ messages in thread* Re: [PATCH qemu v6 6/7] hw/cxl: Support type3 HDM-DB
2026-02-04 12:12 ` [PATCH qemu v6 6/7] hw/cxl: Support type3 HDM-DB Jonathan Cameron
@ 2026-02-04 13:24 ` Michael S. Tsirkin
2026-02-04 13:44 ` Michael S. Tsirkin
0 siblings, 1 reply; 14+ messages in thread
From: Michael S. Tsirkin @ 2026-02-04 13:24 UTC (permalink / raw)
To: Jonathan Cameron
Cc: qemu-devel, Davidlohr Bueso, linuxarm, linux-cxl, Ravi Shankar,
Marcel Apfelbaum, Markus Armbruster, Michael Roth
On Wed, Feb 04, 2026 at 12:12:14PM +0000, Jonathan Cameron wrote:
> From: Davidlohr Bueso <dave@stgolabs.net>
>
> Add basic plumbing for memory expander devices that support Back
> Invalidation. This introduces a 'hdm-db=on|off' parameter and
> exposes the relevant BI RT/Decoder component cachemem registers.
>
> Some noteworthy properties:
> - Devices require enabling Flit mode across the CXL topology.
> - Explicit BI-ID commit is required.
> - HDM decoder support both host and dev coherency models.
>
> Tested-by: Dongjoo Seo <dongjoo.seo1@samsung.com>
> Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
more troubles:
https://gitlab.com/mstredhat/qemu/-/jobs/12984846000
> ---
> v6: Initialize type variable to avoid a false compiler warning
> from some versions of gcc. (Michael Tsirkin)
> ---
> docs/system/devices/cxl.rst | 23 +++++
> include/hw/cxl/cxl_component.h | 54 ++++++++++-
> include/hw/cxl/cxl_device.h | 3 +
> hw/cxl/cxl-component-utils.c | 142 ++++++++++++++++++++++++++--
> hw/mem/cxl_type3.c | 9 +-
> hw/pci-bridge/cxl_downstream.c | 2 +-
> hw/pci-bridge/cxl_root_port.c | 3 +-
> hw/pci-bridge/cxl_upstream.c | 2 +-
> hw/pci-bridge/pci_expander_bridge.c | 2 +-
> 9 files changed, 225 insertions(+), 15 deletions(-)
>
> diff --git a/docs/system/devices/cxl.rst b/docs/system/devices/cxl.rst
> index ca15a0da1c1d..9d0771cdfd73 100644
> --- a/docs/system/devices/cxl.rst
> +++ b/docs/system/devices/cxl.rst
> @@ -384,6 +384,29 @@ An example of 4 devices below a switch suitable for 1, 2 or 4 way interleave::
> -device cxl-type3,bus=swport3,persistent-memdev=cxl-mem3,lsa=cxl-lsa3,id=cxl-pmem3,sn=0x4 \
> -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
>
> +An example of 4 type3 devices with volatile memory below a switch. Two of the devices
> +use HDM-DB for coherence, which requires operating in Flit mode::
> +
> + qemu-system-x86_64 -M q35,cxl=on -m 4G,maxmem=8G,slots=8 -smp 4 \
> + ...
> + -object memory-backend-ram,id=cxl-mem0,share=on,size=256M \
> + -object memory-backend-ram,id=cxl-mem1,share=on,size=256M \
> + -object memory-backend-ram,id=cxl-mem2,share=on,size=256M \
> + -object memory-backend-ram,id=cxl-mem3,share=on,size=256M \
> + -device pxb-cxl,bus_nr=12,bus=pcie.0,id=cxl.1 \
> + -device cxl-rp,port=0,bus=cxl.1,id=root_port0,chassis=0,slot=0 \
> + -device cxl-rp,port=1,bus=cxl.1,id=root_port1,chassis=0,slot=1 \
> + -device cxl-upstream,bus=root_port0,id=us0,x-256b-flit=on \
> + -device cxl-downstream,port=0,bus=us0,id=swport0,chassis=0,slot=4 \
> + -device cxl-type3,bus=swport0,volatile-memdev=cxl-mem0,id=cxl-mem0,sn=0x1,x-256b-flit=on,hdm-db=on \
> + -device cxl-downstream,port=1,bus=us0,id=swport1,chassis=0,slot=5 \
> + -device cxl-type3,bus=swport1,volatile-memdev=cxl-mem1,id=cxl-mem1,sn=0x2,x-256b-flit=on,hdm-db=on \
> + -device cxl-downstream,port=2,bus=us0,id=swport2,chassis=0,slot=6 \
> + -device cxl-type3,bus=swport2,volatile-memdev=cxl-mem2,id=cxl-mem2,sn=0x3 \
> + -device cxl-downstream,port=3,bus=us0,id=swport3,chassis=0,slot=7 \
> + -device cxl-type3,bus=swport3,volatile-memdev=cxl-mem3,id=cxl-mem3,sn=0x4 \
> + -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
> +
> A simple arm/virt example featuring a single direct connected CXL Type 3
> Volatile Memory device::
>
> diff --git a/include/hw/cxl/cxl_component.h b/include/hw/cxl/cxl_component.h
> index 1f167d3ef79b..ffc82202206c 100644
> --- a/include/hw/cxl/cxl_component.h
> +++ b/include/hw/cxl/cxl_component.h
> @@ -67,6 +67,8 @@ CXLx_CAPABILITY_HEADER(LINK, 2)
> CXLx_CAPABILITY_HEADER(HDM, 3)
> CXLx_CAPABILITY_HEADER(EXTSEC, 4)
> CXLx_CAPABILITY_HEADER(SNOOP, 5)
> +CXLx_CAPABILITY_HEADER(BI_RT, 6)
> +CXLx_CAPABILITY_HEADER(BI_DECODER, 7)
>
> /*
> * Capability structures contain the actual registers that the CXL component
> @@ -211,10 +213,55 @@ HDM_DECODER_INIT(3);
> (CXL_IDE_REGISTERS_OFFSET + CXL_IDE_REGISTERS_SIZE)
> #define CXL_SNOOP_REGISTERS_SIZE 0x8
>
> -QEMU_BUILD_BUG_MSG((CXL_SNOOP_REGISTERS_OFFSET +
> - CXL_SNOOP_REGISTERS_SIZE) >= 0x1000,
> +#define CXL_BI_RT_CAP_VERSION 1
> +#define CXL_BI_RT_REGISTERS_OFFSET \
> + (CXL_SNOOP_REGISTERS_OFFSET + CXL_SNOOP_REGISTERS_SIZE)
> +#define CXL_BI_RT_REGISTERS_SIZE 0xC
> +
> +REG32(CXL_BI_RT_CAPABILITY, CXL_BI_RT_REGISTERS_OFFSET)
> + FIELD(CXL_BI_RT_CAPABILITY, EXPLICIT_COMMIT, 0, 1)
> +REG32(CXL_BI_RT_CTRL, CXL_BI_RT_REGISTERS_OFFSET + 0x4)
> + FIELD(CXL_BI_RT_CTRL, COMMIT, 0, 1)
> +REG32(CXL_BI_RT_STATUS, CXL_BI_RT_REGISTERS_OFFSET + 0x8)
> + FIELD(CXL_BI_RT_STATUS, COMMITTED, 0, 1)
> + FIELD(CXL_BI_RT_STATUS, ERR_NOT_COMMITTED, 1, 1)
> + FIELD(CXL_BI_RT_STATUS, COMMIT_TMO_SCALE, 8, 4)
> + FIELD(CXL_BI_RT_STATUS, COMMIT_TMO_BASE, 12, 4)
> +
> +/* CXL r3.2 8.2.4.27 - CXL BI Decoder Capability Structure */
> +#define CXL_BI_DECODER_CAP_VERSION 1
> +#define CXL_BI_DECODER_REGISTERS_OFFSET \
> + (CXL_BI_RT_REGISTERS_OFFSET + CXL_BI_RT_REGISTERS_SIZE)
> +#define CXL_BI_DECODER_REGISTERS_SIZE 0xC
> +
> +REG32(CXL_BI_DECODER_CAPABILITY, CXL_BI_DECODER_REGISTERS_OFFSET)
> + FIELD(CXL_BI_DECODER_CAPABILITY, HDM_D, 0, 1)
> + FIELD(CXL_BI_DECODER_CAPABILITY, EXPLICIT_COMMIT, 1, 1)
> +REG32(CXL_BI_DECODER_CTRL, CXL_BI_DECODER_REGISTERS_OFFSET + 0x4)
> + FIELD(CXL_BI_DECODER_CTRL, BI_FW, 0, 1)
> + FIELD(CXL_BI_DECODER_CTRL, BI_ENABLE, 1, 1)
> + FIELD(CXL_BI_DECODER_CTRL, COMMIT, 2, 1)
> +REG32(CXL_BI_DECODER_STATUS, CXL_BI_DECODER_REGISTERS_OFFSET + 0x8)
> + FIELD(CXL_BI_DECODER_STATUS, COMMITTED, 0, 1)
> + FIELD(CXL_BI_DECODER_STATUS, ERR_NOT_COMMITTED, 1, 1)
> + FIELD(CXL_BI_DECODER_STATUS, COMMIT_TMO_SCALE, 8, 4)
> + FIELD(CXL_BI_DECODER_STATUS, COMMIT_TMO_BASE, 12, 4)
> +
> +QEMU_BUILD_BUG_MSG((CXL_BI_DECODER_REGISTERS_OFFSET +
> + CXL_BI_DECODER_REGISTERS_SIZE) >= 0x1000,
> "No space for registers");
>
> +/* track BI explicit commit handling for route table and decoder */
> +enum {
> + CXL_BISTATE_RT = 0,
> + CXL_BISTATE_DECODER,
> + CXL_BISTATE_MAX
> +};
> +
> +typedef struct bi_state {
> + uint64_t last_commit; /* last 0->1 transition */
> +} BIState;
> +
> typedef struct component_registers {
> /*
> * Main memory region to be registered with QEMU core.
> @@ -259,6 +306,7 @@ typedef struct cxl_component {
> };
>
> CDATObject cdat;
> + BIState bi_state[CXL_BISTATE_MAX];
> } CXLComponentState;
>
> void cxl_component_register_block_init(Object *obj,
> @@ -266,7 +314,7 @@ void cxl_component_register_block_init(Object *obj,
> const char *type);
> void cxl_component_register_init_common(uint32_t *reg_state,
> uint32_t *write_msk,
> - enum reg_type type);
> + enum reg_type type, bool bi);
>
> void cxl_component_create_dvsec(CXLComponentState *cxl_cstate,
> enum reg_type cxl_dev_type, uint16_t length,
> diff --git a/include/hw/cxl/cxl_device.h b/include/hw/cxl/cxl_device.h
> index 7d9236db8c85..393f3122173b 100644
> --- a/include/hw/cxl/cxl_device.h
> +++ b/include/hw/cxl/cxl_device.h
> @@ -770,6 +770,9 @@ struct CXLType3Dev {
> CXLMemSparingReadAttrs rank_sparing_attrs;
> CXLMemSparingWriteAttrs rank_sparing_wr_attrs;
>
> + /* BI flows */
> + bool hdmdb;
> +
> struct dynamic_capacity {
> HostMemoryBackend *host_dc;
> AddressSpace host_dc_as;
> diff --git a/hw/cxl/cxl-component-utils.c b/hw/cxl/cxl-component-utils.c
> index 91770f103a85..a7d36e1128c2 100644
> --- a/hw/cxl/cxl-component-utils.c
> +++ b/hw/cxl/cxl-component-utils.c
> @@ -71,10 +71,40 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
> case 4:
> if (cregs->special_ops && cregs->special_ops->read) {
> return cregs->special_ops->read(cxl_cstate, offset, 4);
> - } else {
> - QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
> - return cregs->cache_mem_registers[offset / 4];
> }
> +
> + QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
> +
> + if (offset == A_CXL_BI_RT_STATUS ||
> + offset == A_CXL_BI_DECODER_STATUS) {
> + int type;
> + uint64_t started;
> +
> + type = (offset == A_CXL_BI_RT_STATUS) ?
> + CXL_BISTATE_RT : CXL_BISTATE_DECODER;
> + started = cxl_cstate->bi_state[type].last_commit;
> +
> + if (started) {
> + uint32_t *cache_mem = cregs->cache_mem_registers;
> + uint32_t val = cache_mem[offset / 4];
> + uint64_t now;
> + int set;
> +
> + now = qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
> + /* arbitrary 100 ms to do the commit */
> + set = !!(now >= started + 100);
> +
> + if (offset == A_CXL_BI_RT_STATUS) {
> + val = FIELD_DP32(val, CXL_BI_RT_STATUS, COMMITTED, set);
> + } else {
> + val = FIELD_DP32(val, CXL_BI_DECODER_STATUS, COMMITTED,
> + set);
> + }
> + stl_le_p((uint8_t *)cache_mem + offset, val);
> + }
> + }
> +
> + return cregs->cache_mem_registers[offset / 4];
> case 8:
> qemu_log_mask(LOG_UNIMP,
> "CXL 8 byte cache mem registers not implemented\n");
> @@ -118,6 +148,47 @@ static void dumb_hdm_handler(CXLComponentState *cxl_cstate, hwaddr offset,
> stl_le_p((uint8_t *)cache_mem + offset, value);
> }
>
> +static void bi_handler(CXLComponentState *cxl_cstate, hwaddr offset,
> + uint32_t value)
> +{
> + ComponentRegisters *cregs = &cxl_cstate->crb;
> + uint32_t sts, *cache_mem = cregs->cache_mem_registers;
> + bool to_commit = false;
> + int type = 0; /* Unused value - work around for compiler warning */
> +
> + switch (offset) {
> + case A_CXL_BI_RT_CTRL:
> + to_commit = FIELD_EX32(value, CXL_BI_RT_CTRL, COMMIT);
> + if (to_commit) {
> + sts = cxl_cache_mem_read_reg(cxl_cstate,
> + R_CXL_BI_RT_STATUS, 4);
> + sts = FIELD_DP32(sts, CXL_BI_RT_STATUS, COMMITTED, 0);
> + stl_le_p((uint8_t *)cache_mem + R_CXL_BI_RT_STATUS, sts);
> + type = CXL_BISTATE_RT;
> + }
> + break;
> + case A_CXL_BI_DECODER_CTRL:
> + to_commit = FIELD_EX32(value, CXL_BI_DECODER_CTRL, COMMIT);
> + if (to_commit) {
> + sts = cxl_cache_mem_read_reg(cxl_cstate,
> + R_CXL_BI_DECODER_STATUS, 4);
> + sts = FIELD_DP32(sts, CXL_BI_DECODER_STATUS, COMMITTED, 0);
> + stl_le_p((uint8_t *)cache_mem + R_CXL_BI_DECODER_STATUS, sts);
> + type = CXL_BISTATE_DECODER;
> + }
> + break;
> + default:
> + break;
> + }
> +
> + if (to_commit) {
> + cxl_cstate->bi_state[type].last_commit =
> + qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
> + }
> +
> + stl_le_p((uint8_t *)cache_mem + offset, value);
> +}
> +
> static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
> unsigned size)
> {
> @@ -141,6 +212,9 @@ static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
> if (offset >= A_CXL_HDM_DECODER_CAPABILITY &&
> offset <= A_CXL_HDM_DECODER3_TARGET_LIST_HI) {
> dumb_hdm_handler(cxl_cstate, offset, value);
> + } else if (offset == A_CXL_BI_RT_CTRL ||
> + offset == A_CXL_BI_DECODER_CTRL) {
> + bi_handler(cxl_cstate, offset, value);
> } else {
> cregs->cache_mem_registers[offset / 4] = value;
> }
> @@ -230,7 +304,7 @@ static void ras_init_common(uint32_t *reg_state, uint32_t *write_msk)
> }
>
> static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> - enum reg_type type)
> + enum reg_type type, bool bi)
> {
> int decoder_count = CXL_HDM_DECODER_COUNT;
> int hdm_inc = R_CXL_HDM_DECODER1_BASE_LO - R_CXL_HDM_DECODER0_BASE_LO;
> @@ -255,7 +329,9 @@ static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> UIO_DECODER_COUNT, 0);
> ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, MEMDATA_NXM_CAP, 0);
> ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY,
> - SUPPORTED_COHERENCY_MODEL, 0); /* Unknown */
> + SUPPORTED_COHERENCY_MODEL,
> + /* host+dev or Unknown */
> + type == CXL2_TYPE3_DEVICE && bi ? 3 : 0);
> ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_GLOBAL_CONTROL,
> HDM_DECODER_ENABLE, 0);
> write_msk[R_CXL_HDM_DECODER_GLOBAL_CONTROL] = 0x3;
> @@ -278,9 +354,43 @@ static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> }
> }
>
> +static void bi_rt_init_common(uint32_t *reg_state, uint32_t *write_msk)
> +{
> + /* switch usp must commit the new BI-ID, timeout of 2secs */
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_CAPABILITY, EXPLICIT_COMMIT, 1);
> +
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_CTRL, COMMIT, 0);
> + write_msk[R_CXL_BI_RT_CTRL] = 0x1;
> +
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMITTED, 0);
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, ERR_NOT_COMMITTED, 0);
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMIT_TMO_SCALE, 0x6);
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMIT_TMO_BASE, 0x2);
> +}
> +
> +static void bi_decoder_init_common(uint32_t *reg_state, uint32_t *write_msk,
> + enum reg_type type)
> +{
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CAPABILITY, HDM_D, 0);
> + /* switch dsp must commit the new BI-ID, timeout of 2secs */
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CAPABILITY, EXPLICIT_COMMIT,
> + (type != CXL2_ROOT_PORT && type != CXL2_TYPE3_DEVICE));
> +
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, BI_FW, 0);
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, BI_ENABLE, 0);
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, COMMIT, 0);
> + write_msk[R_CXL_BI_DECODER_CTRL] = 0x7;
> +
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMITTED, 0);
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, ERR_NOT_COMMITTED, 0);
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMIT_TMO_SCALE, 0x6);
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMIT_TMO_BASE, 0x2);
> +}
> +
> void cxl_component_register_init_common(uint32_t *reg_state,
> uint32_t *write_msk,
> - enum reg_type type)
> + enum reg_type type,
> + bool bi)
> {
> int caps = 0;
>
> @@ -320,7 +430,7 @@ void cxl_component_register_init_common(uint32_t *reg_state,
> case CXL2_LOGICAL_DEVICE:
> /* + HDM */
> init_cap_reg(HDM, 5, 1);
> - hdm_init_common(reg_state, write_msk, type);
> + hdm_init_common(reg_state, write_msk, type, bi);
> /* fallthrough */
> case CXL2_DOWNSTREAM_PORT:
> case CXL2_DEVICE:
> @@ -335,6 +445,24 @@ void cxl_component_register_init_common(uint32_t *reg_state,
> abort();
> }
>
> + /* back invalidate */
> + if (bi) {
> + switch (type) {
> + case CXL2_UPSTREAM_PORT:
> + init_cap_reg(BI_RT, 11, CXL_BI_RT_CAP_VERSION);
> + bi_rt_init_common(reg_state, write_msk);
> + break;
> + case CXL2_ROOT_PORT:
> + case CXL2_DOWNSTREAM_PORT:
> + case CXL2_TYPE3_DEVICE:
> + init_cap_reg(BI_DECODER, 12, CXL_BI_DECODER_CAP_VERSION);
> + bi_decoder_init_common(reg_state, write_msk, type);
> + break;
> + default:
> + break;
> + }
> + }
> +
> ARRAY_FIELD_DP32(reg_state, CXL_CAPABILITY_HEADER, ARRAY_SIZE, caps);
> #undef init_cap_reg
> }
> diff --git a/hw/mem/cxl_type3.c b/hw/mem/cxl_type3.c
> index 3c7ecd8c48bc..3f09c589ae58 100644
> --- a/hw/mem/cxl_type3.c
> +++ b/hw/mem/cxl_type3.c
> @@ -748,6 +748,11 @@ static bool cxl_setup_memory(CXLType3Dev *ct3d, Error **errp)
> return false;
> }
>
> + if (!ct3d->flitmode && ct3d->hdmdb) {
> + error_setg(errp, "hdm-db requires operating in 256b flit");
> + return false;
> + }
> +
> if (ct3d->hostvmem) {
> MemoryRegion *vmr;
> char *v_name;
> @@ -1317,7 +1322,8 @@ static void ct3d_reset(DeviceState *dev)
>
> pcie_cap_fill_link_ep_usp(PCI_DEVICE(dev), ct3d->width, ct3d->speed,
> ct3d->flitmode);
> - cxl_component_register_init_common(reg_state, write_msk, CXL2_TYPE3_DEVICE);
> + cxl_component_register_init_common(reg_state, write_msk,
> + CXL2_TYPE3_DEVICE, ct3d->hdmdb);
> cxl_device_register_init_t3(ct3d, CXL_T3_MSIX_MBOX);
>
> /*
> @@ -1356,6 +1362,7 @@ static const Property ct3_props[] = {
> DEFINE_PROP_PCIE_LINK_WIDTH("x-width", CXLType3Dev,
> width, PCIE_LINK_WIDTH_16),
> DEFINE_PROP_BOOL("x-256b-flit", CXLType3Dev, flitmode, false),
> + DEFINE_PROP_BOOL("hdm-db", CXLType3Dev, hdmdb, false),
> };
>
> static uint64_t get_lsa_size(CXLType3Dev *ct3d)
> diff --git a/hw/pci-bridge/cxl_downstream.c b/hw/pci-bridge/cxl_downstream.c
> index 64086d8ec2f2..320818a8f1ce 100644
> --- a/hw/pci-bridge/cxl_downstream.c
> +++ b/hw/pci-bridge/cxl_downstream.c
> @@ -39,7 +39,7 @@ static void latch_registers(CXLDownstreamPort *dsp)
> uint32_t *write_msk = dsp->cxl_cstate.crb.cache_mem_regs_write_mask;
>
> cxl_component_register_init_common(reg_state, write_msk,
> - CXL2_DOWNSTREAM_PORT);
> + CXL2_DOWNSTREAM_PORT, true);
> }
>
> /* TODO: Look at sharing this code across all CXL port types */
> diff --git a/hw/pci-bridge/cxl_root_port.c b/hw/pci-bridge/cxl_root_port.c
> index 5641048084a4..e2093ac39ee6 100644
> --- a/hw/pci-bridge/cxl_root_port.c
> +++ b/hw/pci-bridge/cxl_root_port.c
> @@ -101,7 +101,8 @@ static void latch_registers(CXLRootPort *crp)
> uint32_t *reg_state = crp->cxl_cstate.crb.cache_mem_registers;
> uint32_t *write_msk = crp->cxl_cstate.crb.cache_mem_regs_write_mask;
>
> - cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT);
> + cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT,
> + true);
> }
>
> static void build_dvsecs(PCIDevice *d, CXLComponentState *cxl)
> diff --git a/hw/pci-bridge/cxl_upstream.c b/hw/pci-bridge/cxl_upstream.c
> index c352d11dc7b7..fb8d19539c9f 100644
> --- a/hw/pci-bridge/cxl_upstream.c
> +++ b/hw/pci-bridge/cxl_upstream.c
> @@ -90,7 +90,7 @@ static void latch_registers(CXLUpstreamPort *usp)
> uint32_t *write_msk = usp->cxl_cstate.crb.cache_mem_regs_write_mask;
>
> cxl_component_register_init_common(reg_state, write_msk,
> - CXL2_UPSTREAM_PORT);
> + CXL2_UPSTREAM_PORT, usp->flitmode);
> ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, TARGET_COUNT, 8);
> }
>
> diff --git a/hw/pci-bridge/pci_expander_bridge.c b/hw/pci-bridge/pci_expander_bridge.c
> index b6e2eb796951..11623a5666f6 100644
> --- a/hw/pci-bridge/pci_expander_bridge.c
> +++ b/hw/pci-bridge/pci_expander_bridge.c
> @@ -300,7 +300,7 @@ static void pxb_cxl_dev_reset(DeviceState *dev)
> uint32_t *write_msk = cxl_cstate->crb.cache_mem_regs_write_mask;
> int dsp_count = 0;
>
> - cxl_component_register_init_common(reg_state, write_msk, CXL2_RC);
> + cxl_component_register_init_common(reg_state, write_msk, CXL2_RC, false);
> /*
> * The CXL specification allows for host bridges with no HDM decoders
> * if they only have a single root port.
> --
> 2.51.0
^ permalink raw reply [flat|nested] 14+ messages in thread* Re: [PATCH qemu v6 6/7] hw/cxl: Support type3 HDM-DB
2026-02-04 13:24 ` Michael S. Tsirkin
@ 2026-02-04 13:44 ` Michael S. Tsirkin
2026-02-04 15:21 ` Jonathan Cameron
0 siblings, 1 reply; 14+ messages in thread
From: Michael S. Tsirkin @ 2026-02-04 13:44 UTC (permalink / raw)
To: Jonathan Cameron
Cc: qemu-devel, Davidlohr Bueso, linuxarm, linux-cxl, Ravi Shankar,
Marcel Apfelbaum, Markus Armbruster, Michael Roth
On Wed, Feb 04, 2026 at 08:24:55AM -0500, Michael S. Tsirkin wrote:
> On Wed, Feb 04, 2026 at 12:12:14PM +0000, Jonathan Cameron wrote:
> > From: Davidlohr Bueso <dave@stgolabs.net>
> >
> > Add basic plumbing for memory expander devices that support Back
> > Invalidation. This introduces a 'hdm-db=on|off' parameter and
> > exposes the relevant BI RT/Decoder component cachemem registers.
> >
> > Some noteworthy properties:
> > - Devices require enabling Flit mode across the CXL topology.
> > - Explicit BI-ID commit is required.
> > - HDM decoder support both host and dev coherency models.
> >
> > Tested-by: Dongjoo Seo <dongjoo.seo1@samsung.com>
> > Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
> > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
>
> more troubles:
> https://gitlab.com/mstredhat/qemu/-/jobs/12984846000
clang just as unhappy:
https://gitlab.com/mstredhat/qemu/-/jobs/12984846060
>
> > ---
> > v6: Initialize type variable to avoid a false compiler warning
> > from some versions of gcc. (Michael Tsirkin)
> > ---
> > docs/system/devices/cxl.rst | 23 +++++
> > include/hw/cxl/cxl_component.h | 54 ++++++++++-
> > include/hw/cxl/cxl_device.h | 3 +
> > hw/cxl/cxl-component-utils.c | 142 ++++++++++++++++++++++++++--
> > hw/mem/cxl_type3.c | 9 +-
> > hw/pci-bridge/cxl_downstream.c | 2 +-
> > hw/pci-bridge/cxl_root_port.c | 3 +-
> > hw/pci-bridge/cxl_upstream.c | 2 +-
> > hw/pci-bridge/pci_expander_bridge.c | 2 +-
> > 9 files changed, 225 insertions(+), 15 deletions(-)
> >
> > diff --git a/docs/system/devices/cxl.rst b/docs/system/devices/cxl.rst
> > index ca15a0da1c1d..9d0771cdfd73 100644
> > --- a/docs/system/devices/cxl.rst
> > +++ b/docs/system/devices/cxl.rst
> > @@ -384,6 +384,29 @@ An example of 4 devices below a switch suitable for 1, 2 or 4 way interleave::
> > -device cxl-type3,bus=swport3,persistent-memdev=cxl-mem3,lsa=cxl-lsa3,id=cxl-pmem3,sn=0x4 \
> > -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
> >
> > +An example of 4 type3 devices with volatile memory below a switch. Two of the devices
> > +use HDM-DB for coherence, which requires operating in Flit mode::
> > +
> > + qemu-system-x86_64 -M q35,cxl=on -m 4G,maxmem=8G,slots=8 -smp 4 \
> > + ...
> > + -object memory-backend-ram,id=cxl-mem0,share=on,size=256M \
> > + -object memory-backend-ram,id=cxl-mem1,share=on,size=256M \
> > + -object memory-backend-ram,id=cxl-mem2,share=on,size=256M \
> > + -object memory-backend-ram,id=cxl-mem3,share=on,size=256M \
> > + -device pxb-cxl,bus_nr=12,bus=pcie.0,id=cxl.1 \
> > + -device cxl-rp,port=0,bus=cxl.1,id=root_port0,chassis=0,slot=0 \
> > + -device cxl-rp,port=1,bus=cxl.1,id=root_port1,chassis=0,slot=1 \
> > + -device cxl-upstream,bus=root_port0,id=us0,x-256b-flit=on \
> > + -device cxl-downstream,port=0,bus=us0,id=swport0,chassis=0,slot=4 \
> > + -device cxl-type3,bus=swport0,volatile-memdev=cxl-mem0,id=cxl-mem0,sn=0x1,x-256b-flit=on,hdm-db=on \
> > + -device cxl-downstream,port=1,bus=us0,id=swport1,chassis=0,slot=5 \
> > + -device cxl-type3,bus=swport1,volatile-memdev=cxl-mem1,id=cxl-mem1,sn=0x2,x-256b-flit=on,hdm-db=on \
> > + -device cxl-downstream,port=2,bus=us0,id=swport2,chassis=0,slot=6 \
> > + -device cxl-type3,bus=swport2,volatile-memdev=cxl-mem2,id=cxl-mem2,sn=0x3 \
> > + -device cxl-downstream,port=3,bus=us0,id=swport3,chassis=0,slot=7 \
> > + -device cxl-type3,bus=swport3,volatile-memdev=cxl-mem3,id=cxl-mem3,sn=0x4 \
> > + -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
> > +
> > A simple arm/virt example featuring a single direct connected CXL Type 3
> > Volatile Memory device::
> >
> > diff --git a/include/hw/cxl/cxl_component.h b/include/hw/cxl/cxl_component.h
> > index 1f167d3ef79b..ffc82202206c 100644
> > --- a/include/hw/cxl/cxl_component.h
> > +++ b/include/hw/cxl/cxl_component.h
> > @@ -67,6 +67,8 @@ CXLx_CAPABILITY_HEADER(LINK, 2)
> > CXLx_CAPABILITY_HEADER(HDM, 3)
> > CXLx_CAPABILITY_HEADER(EXTSEC, 4)
> > CXLx_CAPABILITY_HEADER(SNOOP, 5)
> > +CXLx_CAPABILITY_HEADER(BI_RT, 6)
> > +CXLx_CAPABILITY_HEADER(BI_DECODER, 7)
> >
> > /*
> > * Capability structures contain the actual registers that the CXL component
> > @@ -211,10 +213,55 @@ HDM_DECODER_INIT(3);
> > (CXL_IDE_REGISTERS_OFFSET + CXL_IDE_REGISTERS_SIZE)
> > #define CXL_SNOOP_REGISTERS_SIZE 0x8
> >
> > -QEMU_BUILD_BUG_MSG((CXL_SNOOP_REGISTERS_OFFSET +
> > - CXL_SNOOP_REGISTERS_SIZE) >= 0x1000,
> > +#define CXL_BI_RT_CAP_VERSION 1
> > +#define CXL_BI_RT_REGISTERS_OFFSET \
> > + (CXL_SNOOP_REGISTERS_OFFSET + CXL_SNOOP_REGISTERS_SIZE)
> > +#define CXL_BI_RT_REGISTERS_SIZE 0xC
> > +
> > +REG32(CXL_BI_RT_CAPABILITY, CXL_BI_RT_REGISTERS_OFFSET)
> > + FIELD(CXL_BI_RT_CAPABILITY, EXPLICIT_COMMIT, 0, 1)
> > +REG32(CXL_BI_RT_CTRL, CXL_BI_RT_REGISTERS_OFFSET + 0x4)
> > + FIELD(CXL_BI_RT_CTRL, COMMIT, 0, 1)
> > +REG32(CXL_BI_RT_STATUS, CXL_BI_RT_REGISTERS_OFFSET + 0x8)
> > + FIELD(CXL_BI_RT_STATUS, COMMITTED, 0, 1)
> > + FIELD(CXL_BI_RT_STATUS, ERR_NOT_COMMITTED, 1, 1)
> > + FIELD(CXL_BI_RT_STATUS, COMMIT_TMO_SCALE, 8, 4)
> > + FIELD(CXL_BI_RT_STATUS, COMMIT_TMO_BASE, 12, 4)
> > +
> > +/* CXL r3.2 8.2.4.27 - CXL BI Decoder Capability Structure */
> > +#define CXL_BI_DECODER_CAP_VERSION 1
> > +#define CXL_BI_DECODER_REGISTERS_OFFSET \
> > + (CXL_BI_RT_REGISTERS_OFFSET + CXL_BI_RT_REGISTERS_SIZE)
> > +#define CXL_BI_DECODER_REGISTERS_SIZE 0xC
> > +
> > +REG32(CXL_BI_DECODER_CAPABILITY, CXL_BI_DECODER_REGISTERS_OFFSET)
> > + FIELD(CXL_BI_DECODER_CAPABILITY, HDM_D, 0, 1)
> > + FIELD(CXL_BI_DECODER_CAPABILITY, EXPLICIT_COMMIT, 1, 1)
> > +REG32(CXL_BI_DECODER_CTRL, CXL_BI_DECODER_REGISTERS_OFFSET + 0x4)
> > + FIELD(CXL_BI_DECODER_CTRL, BI_FW, 0, 1)
> > + FIELD(CXL_BI_DECODER_CTRL, BI_ENABLE, 1, 1)
> > + FIELD(CXL_BI_DECODER_CTRL, COMMIT, 2, 1)
> > +REG32(CXL_BI_DECODER_STATUS, CXL_BI_DECODER_REGISTERS_OFFSET + 0x8)
> > + FIELD(CXL_BI_DECODER_STATUS, COMMITTED, 0, 1)
> > + FIELD(CXL_BI_DECODER_STATUS, ERR_NOT_COMMITTED, 1, 1)
> > + FIELD(CXL_BI_DECODER_STATUS, COMMIT_TMO_SCALE, 8, 4)
> > + FIELD(CXL_BI_DECODER_STATUS, COMMIT_TMO_BASE, 12, 4)
> > +
> > +QEMU_BUILD_BUG_MSG((CXL_BI_DECODER_REGISTERS_OFFSET +
> > + CXL_BI_DECODER_REGISTERS_SIZE) >= 0x1000,
> > "No space for registers");
> >
> > +/* track BI explicit commit handling for route table and decoder */
> > +enum {
> > + CXL_BISTATE_RT = 0,
> > + CXL_BISTATE_DECODER,
> > + CXL_BISTATE_MAX
> > +};
> > +
> > +typedef struct bi_state {
> > + uint64_t last_commit; /* last 0->1 transition */
> > +} BIState;
> > +
> > typedef struct component_registers {
> > /*
> > * Main memory region to be registered with QEMU core.
> > @@ -259,6 +306,7 @@ typedef struct cxl_component {
> > };
> >
> > CDATObject cdat;
> > + BIState bi_state[CXL_BISTATE_MAX];
> > } CXLComponentState;
> >
> > void cxl_component_register_block_init(Object *obj,
> > @@ -266,7 +314,7 @@ void cxl_component_register_block_init(Object *obj,
> > const char *type);
> > void cxl_component_register_init_common(uint32_t *reg_state,
> > uint32_t *write_msk,
> > - enum reg_type type);
> > + enum reg_type type, bool bi);
> >
> > void cxl_component_create_dvsec(CXLComponentState *cxl_cstate,
> > enum reg_type cxl_dev_type, uint16_t length,
> > diff --git a/include/hw/cxl/cxl_device.h b/include/hw/cxl/cxl_device.h
> > index 7d9236db8c85..393f3122173b 100644
> > --- a/include/hw/cxl/cxl_device.h
> > +++ b/include/hw/cxl/cxl_device.h
> > @@ -770,6 +770,9 @@ struct CXLType3Dev {
> > CXLMemSparingReadAttrs rank_sparing_attrs;
> > CXLMemSparingWriteAttrs rank_sparing_wr_attrs;
> >
> > + /* BI flows */
> > + bool hdmdb;
> > +
> > struct dynamic_capacity {
> > HostMemoryBackend *host_dc;
> > AddressSpace host_dc_as;
> > diff --git a/hw/cxl/cxl-component-utils.c b/hw/cxl/cxl-component-utils.c
> > index 91770f103a85..a7d36e1128c2 100644
> > --- a/hw/cxl/cxl-component-utils.c
> > +++ b/hw/cxl/cxl-component-utils.c
> > @@ -71,10 +71,40 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
> > case 4:
> > if (cregs->special_ops && cregs->special_ops->read) {
> > return cregs->special_ops->read(cxl_cstate, offset, 4);
> > - } else {
> > - QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
> > - return cregs->cache_mem_registers[offset / 4];
> > }
> > +
> > + QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
> > +
> > + if (offset == A_CXL_BI_RT_STATUS ||
> > + offset == A_CXL_BI_DECODER_STATUS) {
> > + int type;
> > + uint64_t started;
> > +
> > + type = (offset == A_CXL_BI_RT_STATUS) ?
> > + CXL_BISTATE_RT : CXL_BISTATE_DECODER;
> > + started = cxl_cstate->bi_state[type].last_commit;
> > +
> > + if (started) {
> > + uint32_t *cache_mem = cregs->cache_mem_registers;
> > + uint32_t val = cache_mem[offset / 4];
> > + uint64_t now;
> > + int set;
> > +
> > + now = qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
> > + /* arbitrary 100 ms to do the commit */
> > + set = !!(now >= started + 100);
> > +
> > + if (offset == A_CXL_BI_RT_STATUS) {
> > + val = FIELD_DP32(val, CXL_BI_RT_STATUS, COMMITTED, set);
> > + } else {
> > + val = FIELD_DP32(val, CXL_BI_DECODER_STATUS, COMMITTED,
> > + set);
> > + }
> > + stl_le_p((uint8_t *)cache_mem + offset, val);
> > + }
> > + }
> > +
> > + return cregs->cache_mem_registers[offset / 4];
> > case 8:
> > qemu_log_mask(LOG_UNIMP,
> > "CXL 8 byte cache mem registers not implemented\n");
> > @@ -118,6 +148,47 @@ static void dumb_hdm_handler(CXLComponentState *cxl_cstate, hwaddr offset,
> > stl_le_p((uint8_t *)cache_mem + offset, value);
> > }
> >
> > +static void bi_handler(CXLComponentState *cxl_cstate, hwaddr offset,
> > + uint32_t value)
> > +{
> > + ComponentRegisters *cregs = &cxl_cstate->crb;
> > + uint32_t sts, *cache_mem = cregs->cache_mem_registers;
> > + bool to_commit = false;
> > + int type = 0; /* Unused value - work around for compiler warning */
> > +
> > + switch (offset) {
> > + case A_CXL_BI_RT_CTRL:
> > + to_commit = FIELD_EX32(value, CXL_BI_RT_CTRL, COMMIT);
> > + if (to_commit) {
> > + sts = cxl_cache_mem_read_reg(cxl_cstate,
> > + R_CXL_BI_RT_STATUS, 4);
> > + sts = FIELD_DP32(sts, CXL_BI_RT_STATUS, COMMITTED, 0);
> > + stl_le_p((uint8_t *)cache_mem + R_CXL_BI_RT_STATUS, sts);
> > + type = CXL_BISTATE_RT;
> > + }
> > + break;
> > + case A_CXL_BI_DECODER_CTRL:
> > + to_commit = FIELD_EX32(value, CXL_BI_DECODER_CTRL, COMMIT);
> > + if (to_commit) {
> > + sts = cxl_cache_mem_read_reg(cxl_cstate,
> > + R_CXL_BI_DECODER_STATUS, 4);
> > + sts = FIELD_DP32(sts, CXL_BI_DECODER_STATUS, COMMITTED, 0);
> > + stl_le_p((uint8_t *)cache_mem + R_CXL_BI_DECODER_STATUS, sts);
> > + type = CXL_BISTATE_DECODER;
> > + }
> > + break;
> > + default:
> > + break;
> > + }
> > +
> > + if (to_commit) {
> > + cxl_cstate->bi_state[type].last_commit =
> > + qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
> > + }
> > +
> > + stl_le_p((uint8_t *)cache_mem + offset, value);
> > +}
> > +
> > static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
> > unsigned size)
> > {
> > @@ -141,6 +212,9 @@ static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
> > if (offset >= A_CXL_HDM_DECODER_CAPABILITY &&
> > offset <= A_CXL_HDM_DECODER3_TARGET_LIST_HI) {
> > dumb_hdm_handler(cxl_cstate, offset, value);
> > + } else if (offset == A_CXL_BI_RT_CTRL ||
> > + offset == A_CXL_BI_DECODER_CTRL) {
> > + bi_handler(cxl_cstate, offset, value);
> > } else {
> > cregs->cache_mem_registers[offset / 4] = value;
> > }
> > @@ -230,7 +304,7 @@ static void ras_init_common(uint32_t *reg_state, uint32_t *write_msk)
> > }
> >
> > static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > - enum reg_type type)
> > + enum reg_type type, bool bi)
> > {
> > int decoder_count = CXL_HDM_DECODER_COUNT;
> > int hdm_inc = R_CXL_HDM_DECODER1_BASE_LO - R_CXL_HDM_DECODER0_BASE_LO;
> > @@ -255,7 +329,9 @@ static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > UIO_DECODER_COUNT, 0);
> > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, MEMDATA_NXM_CAP, 0);
> > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY,
> > - SUPPORTED_COHERENCY_MODEL, 0); /* Unknown */
> > + SUPPORTED_COHERENCY_MODEL,
> > + /* host+dev or Unknown */
> > + type == CXL2_TYPE3_DEVICE && bi ? 3 : 0);
> > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_GLOBAL_CONTROL,
> > HDM_DECODER_ENABLE, 0);
> > write_msk[R_CXL_HDM_DECODER_GLOBAL_CONTROL] = 0x3;
> > @@ -278,9 +354,43 @@ static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > }
> > }
> >
> > +static void bi_rt_init_common(uint32_t *reg_state, uint32_t *write_msk)
> > +{
> > + /* switch usp must commit the new BI-ID, timeout of 2secs */
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_CAPABILITY, EXPLICIT_COMMIT, 1);
> > +
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_CTRL, COMMIT, 0);
> > + write_msk[R_CXL_BI_RT_CTRL] = 0x1;
> > +
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMITTED, 0);
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, ERR_NOT_COMMITTED, 0);
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMIT_TMO_SCALE, 0x6);
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMIT_TMO_BASE, 0x2);
> > +}
> > +
> > +static void bi_decoder_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > + enum reg_type type)
> > +{
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CAPABILITY, HDM_D, 0);
> > + /* switch dsp must commit the new BI-ID, timeout of 2secs */
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CAPABILITY, EXPLICIT_COMMIT,
> > + (type != CXL2_ROOT_PORT && type != CXL2_TYPE3_DEVICE));
> > +
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, BI_FW, 0);
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, BI_ENABLE, 0);
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, COMMIT, 0);
> > + write_msk[R_CXL_BI_DECODER_CTRL] = 0x7;
> > +
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMITTED, 0);
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, ERR_NOT_COMMITTED, 0);
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMIT_TMO_SCALE, 0x6);
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMIT_TMO_BASE, 0x2);
> > +}
> > +
> > void cxl_component_register_init_common(uint32_t *reg_state,
> > uint32_t *write_msk,
> > - enum reg_type type)
> > + enum reg_type type,
> > + bool bi)
> > {
> > int caps = 0;
> >
> > @@ -320,7 +430,7 @@ void cxl_component_register_init_common(uint32_t *reg_state,
> > case CXL2_LOGICAL_DEVICE:
> > /* + HDM */
> > init_cap_reg(HDM, 5, 1);
> > - hdm_init_common(reg_state, write_msk, type);
> > + hdm_init_common(reg_state, write_msk, type, bi);
> > /* fallthrough */
> > case CXL2_DOWNSTREAM_PORT:
> > case CXL2_DEVICE:
> > @@ -335,6 +445,24 @@ void cxl_component_register_init_common(uint32_t *reg_state,
> > abort();
> > }
> >
> > + /* back invalidate */
> > + if (bi) {
> > + switch (type) {
> > + case CXL2_UPSTREAM_PORT:
> > + init_cap_reg(BI_RT, 11, CXL_BI_RT_CAP_VERSION);
> > + bi_rt_init_common(reg_state, write_msk);
> > + break;
> > + case CXL2_ROOT_PORT:
> > + case CXL2_DOWNSTREAM_PORT:
> > + case CXL2_TYPE3_DEVICE:
> > + init_cap_reg(BI_DECODER, 12, CXL_BI_DECODER_CAP_VERSION);
> > + bi_decoder_init_common(reg_state, write_msk, type);
> > + break;
> > + default:
> > + break;
> > + }
> > + }
> > +
> > ARRAY_FIELD_DP32(reg_state, CXL_CAPABILITY_HEADER, ARRAY_SIZE, caps);
> > #undef init_cap_reg
> > }
> > diff --git a/hw/mem/cxl_type3.c b/hw/mem/cxl_type3.c
> > index 3c7ecd8c48bc..3f09c589ae58 100644
> > --- a/hw/mem/cxl_type3.c
> > +++ b/hw/mem/cxl_type3.c
> > @@ -748,6 +748,11 @@ static bool cxl_setup_memory(CXLType3Dev *ct3d, Error **errp)
> > return false;
> > }
> >
> > + if (!ct3d->flitmode && ct3d->hdmdb) {
> > + error_setg(errp, "hdm-db requires operating in 256b flit");
> > + return false;
> > + }
> > +
> > if (ct3d->hostvmem) {
> > MemoryRegion *vmr;
> > char *v_name;
> > @@ -1317,7 +1322,8 @@ static void ct3d_reset(DeviceState *dev)
> >
> > pcie_cap_fill_link_ep_usp(PCI_DEVICE(dev), ct3d->width, ct3d->speed,
> > ct3d->flitmode);
> > - cxl_component_register_init_common(reg_state, write_msk, CXL2_TYPE3_DEVICE);
> > + cxl_component_register_init_common(reg_state, write_msk,
> > + CXL2_TYPE3_DEVICE, ct3d->hdmdb);
> > cxl_device_register_init_t3(ct3d, CXL_T3_MSIX_MBOX);
> >
> > /*
> > @@ -1356,6 +1362,7 @@ static const Property ct3_props[] = {
> > DEFINE_PROP_PCIE_LINK_WIDTH("x-width", CXLType3Dev,
> > width, PCIE_LINK_WIDTH_16),
> > DEFINE_PROP_BOOL("x-256b-flit", CXLType3Dev, flitmode, false),
> > + DEFINE_PROP_BOOL("hdm-db", CXLType3Dev, hdmdb, false),
> > };
> >
> > static uint64_t get_lsa_size(CXLType3Dev *ct3d)
> > diff --git a/hw/pci-bridge/cxl_downstream.c b/hw/pci-bridge/cxl_downstream.c
> > index 64086d8ec2f2..320818a8f1ce 100644
> > --- a/hw/pci-bridge/cxl_downstream.c
> > +++ b/hw/pci-bridge/cxl_downstream.c
> > @@ -39,7 +39,7 @@ static void latch_registers(CXLDownstreamPort *dsp)
> > uint32_t *write_msk = dsp->cxl_cstate.crb.cache_mem_regs_write_mask;
> >
> > cxl_component_register_init_common(reg_state, write_msk,
> > - CXL2_DOWNSTREAM_PORT);
> > + CXL2_DOWNSTREAM_PORT, true);
> > }
> >
> > /* TODO: Look at sharing this code across all CXL port types */
> > diff --git a/hw/pci-bridge/cxl_root_port.c b/hw/pci-bridge/cxl_root_port.c
> > index 5641048084a4..e2093ac39ee6 100644
> > --- a/hw/pci-bridge/cxl_root_port.c
> > +++ b/hw/pci-bridge/cxl_root_port.c
> > @@ -101,7 +101,8 @@ static void latch_registers(CXLRootPort *crp)
> > uint32_t *reg_state = crp->cxl_cstate.crb.cache_mem_registers;
> > uint32_t *write_msk = crp->cxl_cstate.crb.cache_mem_regs_write_mask;
> >
> > - cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT);
> > + cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT,
> > + true);
> > }
> >
> > static void build_dvsecs(PCIDevice *d, CXLComponentState *cxl)
> > diff --git a/hw/pci-bridge/cxl_upstream.c b/hw/pci-bridge/cxl_upstream.c
> > index c352d11dc7b7..fb8d19539c9f 100644
> > --- a/hw/pci-bridge/cxl_upstream.c
> > +++ b/hw/pci-bridge/cxl_upstream.c
> > @@ -90,7 +90,7 @@ static void latch_registers(CXLUpstreamPort *usp)
> > uint32_t *write_msk = usp->cxl_cstate.crb.cache_mem_regs_write_mask;
> >
> > cxl_component_register_init_common(reg_state, write_msk,
> > - CXL2_UPSTREAM_PORT);
> > + CXL2_UPSTREAM_PORT, usp->flitmode);
> > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, TARGET_COUNT, 8);
> > }
> >
> > diff --git a/hw/pci-bridge/pci_expander_bridge.c b/hw/pci-bridge/pci_expander_bridge.c
> > index b6e2eb796951..11623a5666f6 100644
> > --- a/hw/pci-bridge/pci_expander_bridge.c
> > +++ b/hw/pci-bridge/pci_expander_bridge.c
> > @@ -300,7 +300,7 @@ static void pxb_cxl_dev_reset(DeviceState *dev)
> > uint32_t *write_msk = cxl_cstate->crb.cache_mem_regs_write_mask;
> > int dsp_count = 0;
> >
> > - cxl_component_register_init_common(reg_state, write_msk, CXL2_RC);
> > + cxl_component_register_init_common(reg_state, write_msk, CXL2_RC, false);
> > /*
> > * The CXL specification allows for host bridges with no HDM decoders
> > * if they only have a single root port.
> > --
> > 2.51.0
^ permalink raw reply [flat|nested] 14+ messages in thread* Re: [PATCH qemu v6 6/7] hw/cxl: Support type3 HDM-DB
2026-02-04 13:44 ` Michael S. Tsirkin
@ 2026-02-04 15:21 ` Jonathan Cameron
2026-02-04 15:40 ` Jonathan Cameron
2026-02-04 16:48 ` Michael S. Tsirkin
0 siblings, 2 replies; 14+ messages in thread
From: Jonathan Cameron @ 2026-02-04 15:21 UTC (permalink / raw)
To: Michael S. Tsirkin
Cc: qemu-devel, Davidlohr Bueso, linuxarm, linux-cxl, Ravi Shankar,
Marcel Apfelbaum, Markus Armbruster, Michael Roth
On Wed, 4 Feb 2026 08:44:42 -0500
"Michael S. Tsirkin" <mst@redhat.com> wrote:
> On Wed, Feb 04, 2026 at 08:24:55AM -0500, Michael S. Tsirkin wrote:
> > On Wed, Feb 04, 2026 at 12:12:14PM +0000, Jonathan Cameron wrote:
> > > From: Davidlohr Bueso <dave@stgolabs.net>
> > >
> > > Add basic plumbing for memory expander devices that support Back
> > > Invalidation. This introduces a 'hdm-db=on|off' parameter and
> > > exposes the relevant BI RT/Decoder component cachemem registers.
> > >
> > > Some noteworthy properties:
> > > - Devices require enabling Flit mode across the CXL topology.
> > > - Explicit BI-ID commit is required.
> > > - HDM decoder support both host and dev coherency models.
> > >
> > > Tested-by: Dongjoo Seo <dongjoo.seo1@samsung.com>
> > > Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
> > > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> >
> > more troubles:
> > https://gitlab.com/mstredhat/qemu/-/jobs/12984846000
>
>
> clang just as unhappy:
>
> https://gitlab.com/mstredhat/qemu/-/jobs/12984846060
They both seem to be clang.
Replicated.
Ah. This old gotcha - at one point I got one of my compiler colleagues to report
it as a clang bug but he lost the argument vs the spec. Though I believe
it is being fixed in the C spec longer term. I can't find the thread
now but we did discuss adding local scope in the macro a while back.
Anyhow work around is to add scope to avoid label for the case statement
being followed by _Static_assert()
Despite smelling like a function, it's not and has special rules...
Would you like a v7 or squash the following in?
Thanks
Jonathan
diff --git a/hw/cxl/cxl-component-utils.c b/hw/cxl/cxl-component-utils.c
index a3077184e230..07aabe331c44 100644
--- a/hw/cxl/cxl-component-utils.c
+++ b/hw/cxl/cxl-component-utils.c
@@ -68,7 +68,7 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
ComponentRegisters *cregs = &cxl_cstate->crb;
switch (size) {
- case 4:
+ case 4: {
QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
if (offset == A_CXL_BI_RT_STATUS ||
@@ -101,6 +101,7 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
}
return cregs->cache_mem_registers[offset / 4];
+ }
case 8:
qemu_log_mask(LOG_UNIMP,
"CXL 8 byte cache mem registers not implemented\n");
>
> >
> > > ---
> > > v6: Initialize type variable to avoid a false compiler warning
> > > from some versions of gcc. (Michael Tsirkin)
> > > ---
> > > docs/system/devices/cxl.rst | 23 +++++
> > > include/hw/cxl/cxl_component.h | 54 ++++++++++-
> > > include/hw/cxl/cxl_device.h | 3 +
> > > hw/cxl/cxl-component-utils.c | 142 ++++++++++++++++++++++++++--
> > > hw/mem/cxl_type3.c | 9 +-
> > > hw/pci-bridge/cxl_downstream.c | 2 +-
> > > hw/pci-bridge/cxl_root_port.c | 3 +-
> > > hw/pci-bridge/cxl_upstream.c | 2 +-
> > > hw/pci-bridge/pci_expander_bridge.c | 2 +-
> > > 9 files changed, 225 insertions(+), 15 deletions(-)
> > >
> > > diff --git a/docs/system/devices/cxl.rst b/docs/system/devices/cxl.rst
> > > index ca15a0da1c1d..9d0771cdfd73 100644
> > > --- a/docs/system/devices/cxl.rst
> > > +++ b/docs/system/devices/cxl.rst
> > > @@ -384,6 +384,29 @@ An example of 4 devices below a switch suitable for 1, 2 or 4 way interleave::
> > > -device cxl-type3,bus=swport3,persistent-memdev=cxl-mem3,lsa=cxl-lsa3,id=cxl-pmem3,sn=0x4 \
> > > -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
> > >
> > > +An example of 4 type3 devices with volatile memory below a switch. Two of the devices
> > > +use HDM-DB for coherence, which requires operating in Flit mode::
> > > +
> > > + qemu-system-x86_64 -M q35,cxl=on -m 4G,maxmem=8G,slots=8 -smp 4 \
> > > + ...
> > > + -object memory-backend-ram,id=cxl-mem0,share=on,size=256M \
> > > + -object memory-backend-ram,id=cxl-mem1,share=on,size=256M \
> > > + -object memory-backend-ram,id=cxl-mem2,share=on,size=256M \
> > > + -object memory-backend-ram,id=cxl-mem3,share=on,size=256M \
> > > + -device pxb-cxl,bus_nr=12,bus=pcie.0,id=cxl.1 \
> > > + -device cxl-rp,port=0,bus=cxl.1,id=root_port0,chassis=0,slot=0 \
> > > + -device cxl-rp,port=1,bus=cxl.1,id=root_port1,chassis=0,slot=1 \
> > > + -device cxl-upstream,bus=root_port0,id=us0,x-256b-flit=on \
> > > + -device cxl-downstream,port=0,bus=us0,id=swport0,chassis=0,slot=4 \
> > > + -device cxl-type3,bus=swport0,volatile-memdev=cxl-mem0,id=cxl-mem0,sn=0x1,x-256b-flit=on,hdm-db=on \
> > > + -device cxl-downstream,port=1,bus=us0,id=swport1,chassis=0,slot=5 \
> > > + -device cxl-type3,bus=swport1,volatile-memdev=cxl-mem1,id=cxl-mem1,sn=0x2,x-256b-flit=on,hdm-db=on \
> > > + -device cxl-downstream,port=2,bus=us0,id=swport2,chassis=0,slot=6 \
> > > + -device cxl-type3,bus=swport2,volatile-memdev=cxl-mem2,id=cxl-mem2,sn=0x3 \
> > > + -device cxl-downstream,port=3,bus=us0,id=swport3,chassis=0,slot=7 \
> > > + -device cxl-type3,bus=swport3,volatile-memdev=cxl-mem3,id=cxl-mem3,sn=0x4 \
> > > + -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
> > > +
> > > A simple arm/virt example featuring a single direct connected CXL Type 3
> > > Volatile Memory device::
> > >
> > > diff --git a/include/hw/cxl/cxl_component.h b/include/hw/cxl/cxl_component.h
> > > index 1f167d3ef79b..ffc82202206c 100644
> > > --- a/include/hw/cxl/cxl_component.h
> > > +++ b/include/hw/cxl/cxl_component.h
> > > @@ -67,6 +67,8 @@ CXLx_CAPABILITY_HEADER(LINK, 2)
> > > CXLx_CAPABILITY_HEADER(HDM, 3)
> > > CXLx_CAPABILITY_HEADER(EXTSEC, 4)
> > > CXLx_CAPABILITY_HEADER(SNOOP, 5)
> > > +CXLx_CAPABILITY_HEADER(BI_RT, 6)
> > > +CXLx_CAPABILITY_HEADER(BI_DECODER, 7)
> > >
> > > /*
> > > * Capability structures contain the actual registers that the CXL component
> > > @@ -211,10 +213,55 @@ HDM_DECODER_INIT(3);
> > > (CXL_IDE_REGISTERS_OFFSET + CXL_IDE_REGISTERS_SIZE)
> > > #define CXL_SNOOP_REGISTERS_SIZE 0x8
> > >
> > > -QEMU_BUILD_BUG_MSG((CXL_SNOOP_REGISTERS_OFFSET +
> > > - CXL_SNOOP_REGISTERS_SIZE) >= 0x1000,
> > > +#define CXL_BI_RT_CAP_VERSION 1
> > > +#define CXL_BI_RT_REGISTERS_OFFSET \
> > > + (CXL_SNOOP_REGISTERS_OFFSET + CXL_SNOOP_REGISTERS_SIZE)
> > > +#define CXL_BI_RT_REGISTERS_SIZE 0xC
> > > +
> > > +REG32(CXL_BI_RT_CAPABILITY, CXL_BI_RT_REGISTERS_OFFSET)
> > > + FIELD(CXL_BI_RT_CAPABILITY, EXPLICIT_COMMIT, 0, 1)
> > > +REG32(CXL_BI_RT_CTRL, CXL_BI_RT_REGISTERS_OFFSET + 0x4)
> > > + FIELD(CXL_BI_RT_CTRL, COMMIT, 0, 1)
> > > +REG32(CXL_BI_RT_STATUS, CXL_BI_RT_REGISTERS_OFFSET + 0x8)
> > > + FIELD(CXL_BI_RT_STATUS, COMMITTED, 0, 1)
> > > + FIELD(CXL_BI_RT_STATUS, ERR_NOT_COMMITTED, 1, 1)
> > > + FIELD(CXL_BI_RT_STATUS, COMMIT_TMO_SCALE, 8, 4)
> > > + FIELD(CXL_BI_RT_STATUS, COMMIT_TMO_BASE, 12, 4)
> > > +
> > > +/* CXL r3.2 8.2.4.27 - CXL BI Decoder Capability Structure */
> > > +#define CXL_BI_DECODER_CAP_VERSION 1
> > > +#define CXL_BI_DECODER_REGISTERS_OFFSET \
> > > + (CXL_BI_RT_REGISTERS_OFFSET + CXL_BI_RT_REGISTERS_SIZE)
> > > +#define CXL_BI_DECODER_REGISTERS_SIZE 0xC
> > > +
> > > +REG32(CXL_BI_DECODER_CAPABILITY, CXL_BI_DECODER_REGISTERS_OFFSET)
> > > + FIELD(CXL_BI_DECODER_CAPABILITY, HDM_D, 0, 1)
> > > + FIELD(CXL_BI_DECODER_CAPABILITY, EXPLICIT_COMMIT, 1, 1)
> > > +REG32(CXL_BI_DECODER_CTRL, CXL_BI_DECODER_REGISTERS_OFFSET + 0x4)
> > > + FIELD(CXL_BI_DECODER_CTRL, BI_FW, 0, 1)
> > > + FIELD(CXL_BI_DECODER_CTRL, BI_ENABLE, 1, 1)
> > > + FIELD(CXL_BI_DECODER_CTRL, COMMIT, 2, 1)
> > > +REG32(CXL_BI_DECODER_STATUS, CXL_BI_DECODER_REGISTERS_OFFSET + 0x8)
> > > + FIELD(CXL_BI_DECODER_STATUS, COMMITTED, 0, 1)
> > > + FIELD(CXL_BI_DECODER_STATUS, ERR_NOT_COMMITTED, 1, 1)
> > > + FIELD(CXL_BI_DECODER_STATUS, COMMIT_TMO_SCALE, 8, 4)
> > > + FIELD(CXL_BI_DECODER_STATUS, COMMIT_TMO_BASE, 12, 4)
> > > +
> > > +QEMU_BUILD_BUG_MSG((CXL_BI_DECODER_REGISTERS_OFFSET +
> > > + CXL_BI_DECODER_REGISTERS_SIZE) >= 0x1000,
> > > "No space for registers");
> > >
> > > +/* track BI explicit commit handling for route table and decoder */
> > > +enum {
> > > + CXL_BISTATE_RT = 0,
> > > + CXL_BISTATE_DECODER,
> > > + CXL_BISTATE_MAX
> > > +};
> > > +
> > > +typedef struct bi_state {
> > > + uint64_t last_commit; /* last 0->1 transition */
> > > +} BIState;
> > > +
> > > typedef struct component_registers {
> > > /*
> > > * Main memory region to be registered with QEMU core.
> > > @@ -259,6 +306,7 @@ typedef struct cxl_component {
> > > };
> > >
> > > CDATObject cdat;
> > > + BIState bi_state[CXL_BISTATE_MAX];
> > > } CXLComponentState;
> > >
> > > void cxl_component_register_block_init(Object *obj,
> > > @@ -266,7 +314,7 @@ void cxl_component_register_block_init(Object *obj,
> > > const char *type);
> > > void cxl_component_register_init_common(uint32_t *reg_state,
> > > uint32_t *write_msk,
> > > - enum reg_type type);
> > > + enum reg_type type, bool bi);
> > >
> > > void cxl_component_create_dvsec(CXLComponentState *cxl_cstate,
> > > enum reg_type cxl_dev_type, uint16_t length,
> > > diff --git a/include/hw/cxl/cxl_device.h b/include/hw/cxl/cxl_device.h
> > > index 7d9236db8c85..393f3122173b 100644
> > > --- a/include/hw/cxl/cxl_device.h
> > > +++ b/include/hw/cxl/cxl_device.h
> > > @@ -770,6 +770,9 @@ struct CXLType3Dev {
> > > CXLMemSparingReadAttrs rank_sparing_attrs;
> > > CXLMemSparingWriteAttrs rank_sparing_wr_attrs;
> > >
> > > + /* BI flows */
> > > + bool hdmdb;
> > > +
> > > struct dynamic_capacity {
> > > HostMemoryBackend *host_dc;
> > > AddressSpace host_dc_as;
> > > diff --git a/hw/cxl/cxl-component-utils.c b/hw/cxl/cxl-component-utils.c
> > > index 91770f103a85..a7d36e1128c2 100644
> > > --- a/hw/cxl/cxl-component-utils.c
> > > +++ b/hw/cxl/cxl-component-utils.c
> > > @@ -71,10 +71,40 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
> > > case 4:
> > > if (cregs->special_ops && cregs->special_ops->read) {
> > > return cregs->special_ops->read(cxl_cstate, offset, 4);
> > > - } else {
> > > - QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
> > > - return cregs->cache_mem_registers[offset / 4];
> > > }
> > > +
> > > + QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
> > > +
> > > + if (offset == A_CXL_BI_RT_STATUS ||
> > > + offset == A_CXL_BI_DECODER_STATUS) {
> > > + int type;
> > > + uint64_t started;
> > > +
> > > + type = (offset == A_CXL_BI_RT_STATUS) ?
> > > + CXL_BISTATE_RT : CXL_BISTATE_DECODER;
> > > + started = cxl_cstate->bi_state[type].last_commit;
> > > +
> > > + if (started) {
> > > + uint32_t *cache_mem = cregs->cache_mem_registers;
> > > + uint32_t val = cache_mem[offset / 4];
> > > + uint64_t now;
> > > + int set;
> > > +
> > > + now = qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
> > > + /* arbitrary 100 ms to do the commit */
> > > + set = !!(now >= started + 100);
> > > +
> > > + if (offset == A_CXL_BI_RT_STATUS) {
> > > + val = FIELD_DP32(val, CXL_BI_RT_STATUS, COMMITTED, set);
> > > + } else {
> > > + val = FIELD_DP32(val, CXL_BI_DECODER_STATUS, COMMITTED,
> > > + set);
> > > + }
> > > + stl_le_p((uint8_t *)cache_mem + offset, val);
> > > + }
> > > + }
> > > +
> > > + return cregs->cache_mem_registers[offset / 4];
> > > case 8:
> > > qemu_log_mask(LOG_UNIMP,
> > > "CXL 8 byte cache mem registers not implemented\n");
> > > @@ -118,6 +148,47 @@ static void dumb_hdm_handler(CXLComponentState *cxl_cstate, hwaddr offset,
> > > stl_le_p((uint8_t *)cache_mem + offset, value);
> > > }
> > >
> > > +static void bi_handler(CXLComponentState *cxl_cstate, hwaddr offset,
> > > + uint32_t value)
> > > +{
> > > + ComponentRegisters *cregs = &cxl_cstate->crb;
> > > + uint32_t sts, *cache_mem = cregs->cache_mem_registers;
> > > + bool to_commit = false;
> > > + int type = 0; /* Unused value - work around for compiler warning */
> > > +
> > > + switch (offset) {
> > > + case A_CXL_BI_RT_CTRL:
> > > + to_commit = FIELD_EX32(value, CXL_BI_RT_CTRL, COMMIT);
> > > + if (to_commit) {
> > > + sts = cxl_cache_mem_read_reg(cxl_cstate,
> > > + R_CXL_BI_RT_STATUS, 4);
> > > + sts = FIELD_DP32(sts, CXL_BI_RT_STATUS, COMMITTED, 0);
> > > + stl_le_p((uint8_t *)cache_mem + R_CXL_BI_RT_STATUS, sts);
> > > + type = CXL_BISTATE_RT;
> > > + }
> > > + break;
> > > + case A_CXL_BI_DECODER_CTRL:
> > > + to_commit = FIELD_EX32(value, CXL_BI_DECODER_CTRL, COMMIT);
> > > + if (to_commit) {
> > > + sts = cxl_cache_mem_read_reg(cxl_cstate,
> > > + R_CXL_BI_DECODER_STATUS, 4);
> > > + sts = FIELD_DP32(sts, CXL_BI_DECODER_STATUS, COMMITTED, 0);
> > > + stl_le_p((uint8_t *)cache_mem + R_CXL_BI_DECODER_STATUS, sts);
> > > + type = CXL_BISTATE_DECODER;
> > > + }
> > > + break;
> > > + default:
> > > + break;
> > > + }
> > > +
> > > + if (to_commit) {
> > > + cxl_cstate->bi_state[type].last_commit =
> > > + qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
> > > + }
> > > +
> > > + stl_le_p((uint8_t *)cache_mem + offset, value);
> > > +}
> > > +
> > > static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
> > > unsigned size)
> > > {
> > > @@ -141,6 +212,9 @@ static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
> > > if (offset >= A_CXL_HDM_DECODER_CAPABILITY &&
> > > offset <= A_CXL_HDM_DECODER3_TARGET_LIST_HI) {
> > > dumb_hdm_handler(cxl_cstate, offset, value);
> > > + } else if (offset == A_CXL_BI_RT_CTRL ||
> > > + offset == A_CXL_BI_DECODER_CTRL) {
> > > + bi_handler(cxl_cstate, offset, value);
> > > } else {
> > > cregs->cache_mem_registers[offset / 4] = value;
> > > }
> > > @@ -230,7 +304,7 @@ static void ras_init_common(uint32_t *reg_state, uint32_t *write_msk)
> > > }
> > >
> > > static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > - enum reg_type type)
> > > + enum reg_type type, bool bi)
> > > {
> > > int decoder_count = CXL_HDM_DECODER_COUNT;
> > > int hdm_inc = R_CXL_HDM_DECODER1_BASE_LO - R_CXL_HDM_DECODER0_BASE_LO;
> > > @@ -255,7 +329,9 @@ static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > UIO_DECODER_COUNT, 0);
> > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, MEMDATA_NXM_CAP, 0);
> > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY,
> > > - SUPPORTED_COHERENCY_MODEL, 0); /* Unknown */
> > > + SUPPORTED_COHERENCY_MODEL,
> > > + /* host+dev or Unknown */
> > > + type == CXL2_TYPE3_DEVICE && bi ? 3 : 0);
> > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_GLOBAL_CONTROL,
> > > HDM_DECODER_ENABLE, 0);
> > > write_msk[R_CXL_HDM_DECODER_GLOBAL_CONTROL] = 0x3;
> > > @@ -278,9 +354,43 @@ static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > }
> > > }
> > >
> > > +static void bi_rt_init_common(uint32_t *reg_state, uint32_t *write_msk)
> > > +{
> > > + /* switch usp must commit the new BI-ID, timeout of 2secs */
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_CAPABILITY, EXPLICIT_COMMIT, 1);
> > > +
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_CTRL, COMMIT, 0);
> > > + write_msk[R_CXL_BI_RT_CTRL] = 0x1;
> > > +
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMITTED, 0);
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, ERR_NOT_COMMITTED, 0);
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMIT_TMO_SCALE, 0x6);
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMIT_TMO_BASE, 0x2);
> > > +}
> > > +
> > > +static void bi_decoder_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > + enum reg_type type)
> > > +{
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CAPABILITY, HDM_D, 0);
> > > + /* switch dsp must commit the new BI-ID, timeout of 2secs */
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CAPABILITY, EXPLICIT_COMMIT,
> > > + (type != CXL2_ROOT_PORT && type != CXL2_TYPE3_DEVICE));
> > > +
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, BI_FW, 0);
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, BI_ENABLE, 0);
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, COMMIT, 0);
> > > + write_msk[R_CXL_BI_DECODER_CTRL] = 0x7;
> > > +
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMITTED, 0);
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, ERR_NOT_COMMITTED, 0);
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMIT_TMO_SCALE, 0x6);
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMIT_TMO_BASE, 0x2);
> > > +}
> > > +
> > > void cxl_component_register_init_common(uint32_t *reg_state,
> > > uint32_t *write_msk,
> > > - enum reg_type type)
> > > + enum reg_type type,
> > > + bool bi)
> > > {
> > > int caps = 0;
> > >
> > > @@ -320,7 +430,7 @@ void cxl_component_register_init_common(uint32_t *reg_state,
> > > case CXL2_LOGICAL_DEVICE:
> > > /* + HDM */
> > > init_cap_reg(HDM, 5, 1);
> > > - hdm_init_common(reg_state, write_msk, type);
> > > + hdm_init_common(reg_state, write_msk, type, bi);
> > > /* fallthrough */
> > > case CXL2_DOWNSTREAM_PORT:
> > > case CXL2_DEVICE:
> > > @@ -335,6 +445,24 @@ void cxl_component_register_init_common(uint32_t *reg_state,
> > > abort();
> > > }
> > >
> > > + /* back invalidate */
> > > + if (bi) {
> > > + switch (type) {
> > > + case CXL2_UPSTREAM_PORT:
> > > + init_cap_reg(BI_RT, 11, CXL_BI_RT_CAP_VERSION);
> > > + bi_rt_init_common(reg_state, write_msk);
> > > + break;
> > > + case CXL2_ROOT_PORT:
> > > + case CXL2_DOWNSTREAM_PORT:
> > > + case CXL2_TYPE3_DEVICE:
> > > + init_cap_reg(BI_DECODER, 12, CXL_BI_DECODER_CAP_VERSION);
> > > + bi_decoder_init_common(reg_state, write_msk, type);
> > > + break;
> > > + default:
> > > + break;
> > > + }
> > > + }
> > > +
> > > ARRAY_FIELD_DP32(reg_state, CXL_CAPABILITY_HEADER, ARRAY_SIZE, caps);
> > > #undef init_cap_reg
> > > }
> > > diff --git a/hw/mem/cxl_type3.c b/hw/mem/cxl_type3.c
> > > index 3c7ecd8c48bc..3f09c589ae58 100644
> > > --- a/hw/mem/cxl_type3.c
> > > +++ b/hw/mem/cxl_type3.c
> > > @@ -748,6 +748,11 @@ static bool cxl_setup_memory(CXLType3Dev *ct3d, Error **errp)
> > > return false;
> > > }
> > >
> > > + if (!ct3d->flitmode && ct3d->hdmdb) {
> > > + error_setg(errp, "hdm-db requires operating in 256b flit");
> > > + return false;
> > > + }
> > > +
> > > if (ct3d->hostvmem) {
> > > MemoryRegion *vmr;
> > > char *v_name;
> > > @@ -1317,7 +1322,8 @@ static void ct3d_reset(DeviceState *dev)
> > >
> > > pcie_cap_fill_link_ep_usp(PCI_DEVICE(dev), ct3d->width, ct3d->speed,
> > > ct3d->flitmode);
> > > - cxl_component_register_init_common(reg_state, write_msk, CXL2_TYPE3_DEVICE);
> > > + cxl_component_register_init_common(reg_state, write_msk,
> > > + CXL2_TYPE3_DEVICE, ct3d->hdmdb);
> > > cxl_device_register_init_t3(ct3d, CXL_T3_MSIX_MBOX);
> > >
> > > /*
> > > @@ -1356,6 +1362,7 @@ static const Property ct3_props[] = {
> > > DEFINE_PROP_PCIE_LINK_WIDTH("x-width", CXLType3Dev,
> > > width, PCIE_LINK_WIDTH_16),
> > > DEFINE_PROP_BOOL("x-256b-flit", CXLType3Dev, flitmode, false),
> > > + DEFINE_PROP_BOOL("hdm-db", CXLType3Dev, hdmdb, false),
> > > };
> > >
> > > static uint64_t get_lsa_size(CXLType3Dev *ct3d)
> > > diff --git a/hw/pci-bridge/cxl_downstream.c b/hw/pci-bridge/cxl_downstream.c
> > > index 64086d8ec2f2..320818a8f1ce 100644
> > > --- a/hw/pci-bridge/cxl_downstream.c
> > > +++ b/hw/pci-bridge/cxl_downstream.c
> > > @@ -39,7 +39,7 @@ static void latch_registers(CXLDownstreamPort *dsp)
> > > uint32_t *write_msk = dsp->cxl_cstate.crb.cache_mem_regs_write_mask;
> > >
> > > cxl_component_register_init_common(reg_state, write_msk,
> > > - CXL2_DOWNSTREAM_PORT);
> > > + CXL2_DOWNSTREAM_PORT, true);
> > > }
> > >
> > > /* TODO: Look at sharing this code across all CXL port types */
> > > diff --git a/hw/pci-bridge/cxl_root_port.c b/hw/pci-bridge/cxl_root_port.c
> > > index 5641048084a4..e2093ac39ee6 100644
> > > --- a/hw/pci-bridge/cxl_root_port.c
> > > +++ b/hw/pci-bridge/cxl_root_port.c
> > > @@ -101,7 +101,8 @@ static void latch_registers(CXLRootPort *crp)
> > > uint32_t *reg_state = crp->cxl_cstate.crb.cache_mem_registers;
> > > uint32_t *write_msk = crp->cxl_cstate.crb.cache_mem_regs_write_mask;
> > >
> > > - cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT);
> > > + cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT,
> > > + true);
> > > }
> > >
> > > static void build_dvsecs(PCIDevice *d, CXLComponentState *cxl)
> > > diff --git a/hw/pci-bridge/cxl_upstream.c b/hw/pci-bridge/cxl_upstream.c
> > > index c352d11dc7b7..fb8d19539c9f 100644
> > > --- a/hw/pci-bridge/cxl_upstream.c
> > > +++ b/hw/pci-bridge/cxl_upstream.c
> > > @@ -90,7 +90,7 @@ static void latch_registers(CXLUpstreamPort *usp)
> > > uint32_t *write_msk = usp->cxl_cstate.crb.cache_mem_regs_write_mask;
> > >
> > > cxl_component_register_init_common(reg_state, write_msk,
> > > - CXL2_UPSTREAM_PORT);
> > > + CXL2_UPSTREAM_PORT, usp->flitmode);
> > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, TARGET_COUNT, 8);
> > > }
> > >
> > > diff --git a/hw/pci-bridge/pci_expander_bridge.c b/hw/pci-bridge/pci_expander_bridge.c
> > > index b6e2eb796951..11623a5666f6 100644
> > > --- a/hw/pci-bridge/pci_expander_bridge.c
> > > +++ b/hw/pci-bridge/pci_expander_bridge.c
> > > @@ -300,7 +300,7 @@ static void pxb_cxl_dev_reset(DeviceState *dev)
> > > uint32_t *write_msk = cxl_cstate->crb.cache_mem_regs_write_mask;
> > > int dsp_count = 0;
> > >
> > > - cxl_component_register_init_common(reg_state, write_msk, CXL2_RC);
> > > + cxl_component_register_init_common(reg_state, write_msk, CXL2_RC, false);
> > > /*
> > > * The CXL specification allows for host bridges with no HDM decoders
> > > * if they only have a single root port.
> > > --
> > > 2.51.0
>
>
^ permalink raw reply related [flat|nested] 14+ messages in thread* Re: [PATCH qemu v6 6/7] hw/cxl: Support type3 HDM-DB
2026-02-04 15:21 ` Jonathan Cameron
@ 2026-02-04 15:40 ` Jonathan Cameron
2026-02-04 15:50 ` Jonathan Cameron
2026-02-04 16:48 ` Michael S. Tsirkin
1 sibling, 1 reply; 14+ messages in thread
From: Jonathan Cameron @ 2026-02-04 15:40 UTC (permalink / raw)
To: Jonathan Cameron via qemu development, linuxarm
Cc: Jonathan Cameron, Michael S. Tsirkin, Davidlohr Bueso, linux-cxl,
Ravi Shankar, Marcel Apfelbaum, Markus Armbruster, Michael Roth
On Wed, 4 Feb 2026 15:21:02 +0000
Jonathan Cameron via qemu development <qemu-devel@nongnu.org> wrote:
> On Wed, 4 Feb 2026 08:44:42 -0500
> "Michael S. Tsirkin" <mst@redhat.com> wrote:
>
> > On Wed, Feb 04, 2026 at 08:24:55AM -0500, Michael S. Tsirkin wrote:
> > > On Wed, Feb 04, 2026 at 12:12:14PM +0000, Jonathan Cameron wrote:
> > > > From: Davidlohr Bueso <dave@stgolabs.net>
> > > >
> > > > Add basic plumbing for memory expander devices that support Back
> > > > Invalidation. This introduces a 'hdm-db=on|off' parameter and
> > > > exposes the relevant BI RT/Decoder component cachemem registers.
> > > >
> > > > Some noteworthy properties:
> > > > - Devices require enabling Flit mode across the CXL topology.
> > > > - Explicit BI-ID commit is required.
> > > > - HDM decoder support both host and dev coherency models.
> > > >
> > > > Tested-by: Dongjoo Seo <dongjoo.seo1@samsung.com>
> > > > Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
> > > > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > >
> > > more troubles:
> > > https://gitlab.com/mstredhat/qemu/-/jobs/12984846000
> >
> >
> > clang just as unhappy:
> >
> > https://gitlab.com/mstredhat/qemu/-/jobs/12984846060
> They both seem to be clang.
>
> Replicated.
>
> Ah. This old gotcha - at one point I got one of my compiler colleagues to report
> it as a clang bug but he lost the argument vs the spec. Though I believe
> it is being fixed in the C spec longer term. I can't find the thread
> now but we did discuss adding local scope in the macro a while back.
>
> Anyhow work around is to add scope to avoid label for the case statement
> being followed by _Static_assert()
> Despite smelling like a function, it's not and has special rules...
>
> Would you like a v7 or squash the following in?
Or. The problem only actually occurs after the next patch (which happens
to bring the _static assert to the top of the case statement.)
So drop patch 7 and I'll revisit just that little one at a later date.
> Thanks
>
> Jonathan
>
>
> diff --git a/hw/cxl/cxl-component-utils.c b/hw/cxl/cxl-component-utils.c
> index a3077184e230..07aabe331c44 100644
> --- a/hw/cxl/cxl-component-utils.c
> +++ b/hw/cxl/cxl-component-utils.c
> @@ -68,7 +68,7 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
> ComponentRegisters *cregs = &cxl_cstate->crb;
>
> switch (size) {
> - case 4:
> + case 4: {
> QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
>
> if (offset == A_CXL_BI_RT_STATUS ||
> @@ -101,6 +101,7 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
> }
>
> return cregs->cache_mem_registers[offset / 4];
> + }
> case 8:
> qemu_log_mask(LOG_UNIMP,
> "CXL 8 byte cache mem registers not implemented\n");
>
>
> >
> > >
> > > > ---
> > > > v6: Initialize type variable to avoid a false compiler warning
> > > > from some versions of gcc. (Michael Tsirkin)
> > > > ---
> > > > docs/system/devices/cxl.rst | 23 +++++
> > > > include/hw/cxl/cxl_component.h | 54 ++++++++++-
> > > > include/hw/cxl/cxl_device.h | 3 +
> > > > hw/cxl/cxl-component-utils.c | 142 ++++++++++++++++++++++++++--
> > > > hw/mem/cxl_type3.c | 9 +-
> > > > hw/pci-bridge/cxl_downstream.c | 2 +-
> > > > hw/pci-bridge/cxl_root_port.c | 3 +-
> > > > hw/pci-bridge/cxl_upstream.c | 2 +-
> > > > hw/pci-bridge/pci_expander_bridge.c | 2 +-
> > > > 9 files changed, 225 insertions(+), 15 deletions(-)
> > > >
> > > > diff --git a/docs/system/devices/cxl.rst b/docs/system/devices/cxl.rst
> > > > index ca15a0da1c1d..9d0771cdfd73 100644
> > > > --- a/docs/system/devices/cxl.rst
> > > > +++ b/docs/system/devices/cxl.rst
> > > > @@ -384,6 +384,29 @@ An example of 4 devices below a switch suitable for 1, 2 or 4 way interleave::
> > > > -device cxl-type3,bus=swport3,persistent-memdev=cxl-mem3,lsa=cxl-lsa3,id=cxl-pmem3,sn=0x4 \
> > > > -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
> > > >
> > > > +An example of 4 type3 devices with volatile memory below a switch. Two of the devices
> > > > +use HDM-DB for coherence, which requires operating in Flit mode::
> > > > +
> > > > + qemu-system-x86_64 -M q35,cxl=on -m 4G,maxmem=8G,slots=8 -smp 4 \
> > > > + ...
> > > > + -object memory-backend-ram,id=cxl-mem0,share=on,size=256M \
> > > > + -object memory-backend-ram,id=cxl-mem1,share=on,size=256M \
> > > > + -object memory-backend-ram,id=cxl-mem2,share=on,size=256M \
> > > > + -object memory-backend-ram,id=cxl-mem3,share=on,size=256M \
> > > > + -device pxb-cxl,bus_nr=12,bus=pcie.0,id=cxl.1 \
> > > > + -device cxl-rp,port=0,bus=cxl.1,id=root_port0,chassis=0,slot=0 \
> > > > + -device cxl-rp,port=1,bus=cxl.1,id=root_port1,chassis=0,slot=1 \
> > > > + -device cxl-upstream,bus=root_port0,id=us0,x-256b-flit=on \
> > > > + -device cxl-downstream,port=0,bus=us0,id=swport0,chassis=0,slot=4 \
> > > > + -device cxl-type3,bus=swport0,volatile-memdev=cxl-mem0,id=cxl-mem0,sn=0x1,x-256b-flit=on,hdm-db=on \
> > > > + -device cxl-downstream,port=1,bus=us0,id=swport1,chassis=0,slot=5 \
> > > > + -device cxl-type3,bus=swport1,volatile-memdev=cxl-mem1,id=cxl-mem1,sn=0x2,x-256b-flit=on,hdm-db=on \
> > > > + -device cxl-downstream,port=2,bus=us0,id=swport2,chassis=0,slot=6 \
> > > > + -device cxl-type3,bus=swport2,volatile-memdev=cxl-mem2,id=cxl-mem2,sn=0x3 \
> > > > + -device cxl-downstream,port=3,bus=us0,id=swport3,chassis=0,slot=7 \
> > > > + -device cxl-type3,bus=swport3,volatile-memdev=cxl-mem3,id=cxl-mem3,sn=0x4 \
> > > > + -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
> > > > +
> > > > A simple arm/virt example featuring a single direct connected CXL Type 3
> > > > Volatile Memory device::
> > > >
> > > > diff --git a/include/hw/cxl/cxl_component.h b/include/hw/cxl/cxl_component.h
> > > > index 1f167d3ef79b..ffc82202206c 100644
> > > > --- a/include/hw/cxl/cxl_component.h
> > > > +++ b/include/hw/cxl/cxl_component.h
> > > > @@ -67,6 +67,8 @@ CXLx_CAPABILITY_HEADER(LINK, 2)
> > > > CXLx_CAPABILITY_HEADER(HDM, 3)
> > > > CXLx_CAPABILITY_HEADER(EXTSEC, 4)
> > > > CXLx_CAPABILITY_HEADER(SNOOP, 5)
> > > > +CXLx_CAPABILITY_HEADER(BI_RT, 6)
> > > > +CXLx_CAPABILITY_HEADER(BI_DECODER, 7)
> > > >
> > > > /*
> > > > * Capability structures contain the actual registers that the CXL component
> > > > @@ -211,10 +213,55 @@ HDM_DECODER_INIT(3);
> > > > (CXL_IDE_REGISTERS_OFFSET + CXL_IDE_REGISTERS_SIZE)
> > > > #define CXL_SNOOP_REGISTERS_SIZE 0x8
> > > >
> > > > -QEMU_BUILD_BUG_MSG((CXL_SNOOP_REGISTERS_OFFSET +
> > > > - CXL_SNOOP_REGISTERS_SIZE) >= 0x1000,
> > > > +#define CXL_BI_RT_CAP_VERSION 1
> > > > +#define CXL_BI_RT_REGISTERS_OFFSET \
> > > > + (CXL_SNOOP_REGISTERS_OFFSET + CXL_SNOOP_REGISTERS_SIZE)
> > > > +#define CXL_BI_RT_REGISTERS_SIZE 0xC
> > > > +
> > > > +REG32(CXL_BI_RT_CAPABILITY, CXL_BI_RT_REGISTERS_OFFSET)
> > > > + FIELD(CXL_BI_RT_CAPABILITY, EXPLICIT_COMMIT, 0, 1)
> > > > +REG32(CXL_BI_RT_CTRL, CXL_BI_RT_REGISTERS_OFFSET + 0x4)
> > > > + FIELD(CXL_BI_RT_CTRL, COMMIT, 0, 1)
> > > > +REG32(CXL_BI_RT_STATUS, CXL_BI_RT_REGISTERS_OFFSET + 0x8)
> > > > + FIELD(CXL_BI_RT_STATUS, COMMITTED, 0, 1)
> > > > + FIELD(CXL_BI_RT_STATUS, ERR_NOT_COMMITTED, 1, 1)
> > > > + FIELD(CXL_BI_RT_STATUS, COMMIT_TMO_SCALE, 8, 4)
> > > > + FIELD(CXL_BI_RT_STATUS, COMMIT_TMO_BASE, 12, 4)
> > > > +
> > > > +/* CXL r3.2 8.2.4.27 - CXL BI Decoder Capability Structure */
> > > > +#define CXL_BI_DECODER_CAP_VERSION 1
> > > > +#define CXL_BI_DECODER_REGISTERS_OFFSET \
> > > > + (CXL_BI_RT_REGISTERS_OFFSET + CXL_BI_RT_REGISTERS_SIZE)
> > > > +#define CXL_BI_DECODER_REGISTERS_SIZE 0xC
> > > > +
> > > > +REG32(CXL_BI_DECODER_CAPABILITY, CXL_BI_DECODER_REGISTERS_OFFSET)
> > > > + FIELD(CXL_BI_DECODER_CAPABILITY, HDM_D, 0, 1)
> > > > + FIELD(CXL_BI_DECODER_CAPABILITY, EXPLICIT_COMMIT, 1, 1)
> > > > +REG32(CXL_BI_DECODER_CTRL, CXL_BI_DECODER_REGISTERS_OFFSET + 0x4)
> > > > + FIELD(CXL_BI_DECODER_CTRL, BI_FW, 0, 1)
> > > > + FIELD(CXL_BI_DECODER_CTRL, BI_ENABLE, 1, 1)
> > > > + FIELD(CXL_BI_DECODER_CTRL, COMMIT, 2, 1)
> > > > +REG32(CXL_BI_DECODER_STATUS, CXL_BI_DECODER_REGISTERS_OFFSET + 0x8)
> > > > + FIELD(CXL_BI_DECODER_STATUS, COMMITTED, 0, 1)
> > > > + FIELD(CXL_BI_DECODER_STATUS, ERR_NOT_COMMITTED, 1, 1)
> > > > + FIELD(CXL_BI_DECODER_STATUS, COMMIT_TMO_SCALE, 8, 4)
> > > > + FIELD(CXL_BI_DECODER_STATUS, COMMIT_TMO_BASE, 12, 4)
> > > > +
> > > > +QEMU_BUILD_BUG_MSG((CXL_BI_DECODER_REGISTERS_OFFSET +
> > > > + CXL_BI_DECODER_REGISTERS_SIZE) >= 0x1000,
> > > > "No space for registers");
> > > >
> > > > +/* track BI explicit commit handling for route table and decoder */
> > > > +enum {
> > > > + CXL_BISTATE_RT = 0,
> > > > + CXL_BISTATE_DECODER,
> > > > + CXL_BISTATE_MAX
> > > > +};
> > > > +
> > > > +typedef struct bi_state {
> > > > + uint64_t last_commit; /* last 0->1 transition */
> > > > +} BIState;
> > > > +
> > > > typedef struct component_registers {
> > > > /*
> > > > * Main memory region to be registered with QEMU core.
> > > > @@ -259,6 +306,7 @@ typedef struct cxl_component {
> > > > };
> > > >
> > > > CDATObject cdat;
> > > > + BIState bi_state[CXL_BISTATE_MAX];
> > > > } CXLComponentState;
> > > >
> > > > void cxl_component_register_block_init(Object *obj,
> > > > @@ -266,7 +314,7 @@ void cxl_component_register_block_init(Object *obj,
> > > > const char *type);
> > > > void cxl_component_register_init_common(uint32_t *reg_state,
> > > > uint32_t *write_msk,
> > > > - enum reg_type type);
> > > > + enum reg_type type, bool bi);
> > > >
> > > > void cxl_component_create_dvsec(CXLComponentState *cxl_cstate,
> > > > enum reg_type cxl_dev_type, uint16_t length,
> > > > diff --git a/include/hw/cxl/cxl_device.h b/include/hw/cxl/cxl_device.h
> > > > index 7d9236db8c85..393f3122173b 100644
> > > > --- a/include/hw/cxl/cxl_device.h
> > > > +++ b/include/hw/cxl/cxl_device.h
> > > > @@ -770,6 +770,9 @@ struct CXLType3Dev {
> > > > CXLMemSparingReadAttrs rank_sparing_attrs;
> > > > CXLMemSparingWriteAttrs rank_sparing_wr_attrs;
> > > >
> > > > + /* BI flows */
> > > > + bool hdmdb;
> > > > +
> > > > struct dynamic_capacity {
> > > > HostMemoryBackend *host_dc;
> > > > AddressSpace host_dc_as;
> > > > diff --git a/hw/cxl/cxl-component-utils.c b/hw/cxl/cxl-component-utils.c
> > > > index 91770f103a85..a7d36e1128c2 100644
> > > > --- a/hw/cxl/cxl-component-utils.c
> > > > +++ b/hw/cxl/cxl-component-utils.c
> > > > @@ -71,10 +71,40 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
> > > > case 4:
> > > > if (cregs->special_ops && cregs->special_ops->read) {
> > > > return cregs->special_ops->read(cxl_cstate, offset, 4);
> > > > - } else {
> > > > - QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
> > > > - return cregs->cache_mem_registers[offset / 4];
> > > > }
> > > > +
> > > > + QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
> > > > +
> > > > + if (offset == A_CXL_BI_RT_STATUS ||
> > > > + offset == A_CXL_BI_DECODER_STATUS) {
> > > > + int type;
> > > > + uint64_t started;
> > > > +
> > > > + type = (offset == A_CXL_BI_RT_STATUS) ?
> > > > + CXL_BISTATE_RT : CXL_BISTATE_DECODER;
> > > > + started = cxl_cstate->bi_state[type].last_commit;
> > > > +
> > > > + if (started) {
> > > > + uint32_t *cache_mem = cregs->cache_mem_registers;
> > > > + uint32_t val = cache_mem[offset / 4];
> > > > + uint64_t now;
> > > > + int set;
> > > > +
> > > > + now = qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
> > > > + /* arbitrary 100 ms to do the commit */
> > > > + set = !!(now >= started + 100);
> > > > +
> > > > + if (offset == A_CXL_BI_RT_STATUS) {
> > > > + val = FIELD_DP32(val, CXL_BI_RT_STATUS, COMMITTED, set);
> > > > + } else {
> > > > + val = FIELD_DP32(val, CXL_BI_DECODER_STATUS, COMMITTED,
> > > > + set);
> > > > + }
> > > > + stl_le_p((uint8_t *)cache_mem + offset, val);
> > > > + }
> > > > + }
> > > > +
> > > > + return cregs->cache_mem_registers[offset / 4];
> > > > case 8:
> > > > qemu_log_mask(LOG_UNIMP,
> > > > "CXL 8 byte cache mem registers not implemented\n");
> > > > @@ -118,6 +148,47 @@ static void dumb_hdm_handler(CXLComponentState *cxl_cstate, hwaddr offset,
> > > > stl_le_p((uint8_t *)cache_mem + offset, value);
> > > > }
> > > >
> > > > +static void bi_handler(CXLComponentState *cxl_cstate, hwaddr offset,
> > > > + uint32_t value)
> > > > +{
> > > > + ComponentRegisters *cregs = &cxl_cstate->crb;
> > > > + uint32_t sts, *cache_mem = cregs->cache_mem_registers;
> > > > + bool to_commit = false;
> > > > + int type = 0; /* Unused value - work around for compiler warning */
> > > > +
> > > > + switch (offset) {
> > > > + case A_CXL_BI_RT_CTRL:
> > > > + to_commit = FIELD_EX32(value, CXL_BI_RT_CTRL, COMMIT);
> > > > + if (to_commit) {
> > > > + sts = cxl_cache_mem_read_reg(cxl_cstate,
> > > > + R_CXL_BI_RT_STATUS, 4);
> > > > + sts = FIELD_DP32(sts, CXL_BI_RT_STATUS, COMMITTED, 0);
> > > > + stl_le_p((uint8_t *)cache_mem + R_CXL_BI_RT_STATUS, sts);
> > > > + type = CXL_BISTATE_RT;
> > > > + }
> > > > + break;
> > > > + case A_CXL_BI_DECODER_CTRL:
> > > > + to_commit = FIELD_EX32(value, CXL_BI_DECODER_CTRL, COMMIT);
> > > > + if (to_commit) {
> > > > + sts = cxl_cache_mem_read_reg(cxl_cstate,
> > > > + R_CXL_BI_DECODER_STATUS, 4);
> > > > + sts = FIELD_DP32(sts, CXL_BI_DECODER_STATUS, COMMITTED, 0);
> > > > + stl_le_p((uint8_t *)cache_mem + R_CXL_BI_DECODER_STATUS, sts);
> > > > + type = CXL_BISTATE_DECODER;
> > > > + }
> > > > + break;
> > > > + default:
> > > > + break;
> > > > + }
> > > > +
> > > > + if (to_commit) {
> > > > + cxl_cstate->bi_state[type].last_commit =
> > > > + qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
> > > > + }
> > > > +
> > > > + stl_le_p((uint8_t *)cache_mem + offset, value);
> > > > +}
> > > > +
> > > > static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
> > > > unsigned size)
> > > > {
> > > > @@ -141,6 +212,9 @@ static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
> > > > if (offset >= A_CXL_HDM_DECODER_CAPABILITY &&
> > > > offset <= A_CXL_HDM_DECODER3_TARGET_LIST_HI) {
> > > > dumb_hdm_handler(cxl_cstate, offset, value);
> > > > + } else if (offset == A_CXL_BI_RT_CTRL ||
> > > > + offset == A_CXL_BI_DECODER_CTRL) {
> > > > + bi_handler(cxl_cstate, offset, value);
> > > > } else {
> > > > cregs->cache_mem_registers[offset / 4] = value;
> > > > }
> > > > @@ -230,7 +304,7 @@ static void ras_init_common(uint32_t *reg_state, uint32_t *write_msk)
> > > > }
> > > >
> > > > static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > > - enum reg_type type)
> > > > + enum reg_type type, bool bi)
> > > > {
> > > > int decoder_count = CXL_HDM_DECODER_COUNT;
> > > > int hdm_inc = R_CXL_HDM_DECODER1_BASE_LO - R_CXL_HDM_DECODER0_BASE_LO;
> > > > @@ -255,7 +329,9 @@ static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > > UIO_DECODER_COUNT, 0);
> > > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, MEMDATA_NXM_CAP, 0);
> > > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY,
> > > > - SUPPORTED_COHERENCY_MODEL, 0); /* Unknown */
> > > > + SUPPORTED_COHERENCY_MODEL,
> > > > + /* host+dev or Unknown */
> > > > + type == CXL2_TYPE3_DEVICE && bi ? 3 : 0);
> > > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_GLOBAL_CONTROL,
> > > > HDM_DECODER_ENABLE, 0);
> > > > write_msk[R_CXL_HDM_DECODER_GLOBAL_CONTROL] = 0x3;
> > > > @@ -278,9 +354,43 @@ static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > > }
> > > > }
> > > >
> > > > +static void bi_rt_init_common(uint32_t *reg_state, uint32_t *write_msk)
> > > > +{
> > > > + /* switch usp must commit the new BI-ID, timeout of 2secs */
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_CAPABILITY, EXPLICIT_COMMIT, 1);
> > > > +
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_CTRL, COMMIT, 0);
> > > > + write_msk[R_CXL_BI_RT_CTRL] = 0x1;
> > > > +
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMITTED, 0);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, ERR_NOT_COMMITTED, 0);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMIT_TMO_SCALE, 0x6);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMIT_TMO_BASE, 0x2);
> > > > +}
> > > > +
> > > > +static void bi_decoder_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > > + enum reg_type type)
> > > > +{
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CAPABILITY, HDM_D, 0);
> > > > + /* switch dsp must commit the new BI-ID, timeout of 2secs */
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CAPABILITY, EXPLICIT_COMMIT,
> > > > + (type != CXL2_ROOT_PORT && type != CXL2_TYPE3_DEVICE));
> > > > +
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, BI_FW, 0);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, BI_ENABLE, 0);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, COMMIT, 0);
> > > > + write_msk[R_CXL_BI_DECODER_CTRL] = 0x7;
> > > > +
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMITTED, 0);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, ERR_NOT_COMMITTED, 0);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMIT_TMO_SCALE, 0x6);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMIT_TMO_BASE, 0x2);
> > > > +}
> > > > +
> > > > void cxl_component_register_init_common(uint32_t *reg_state,
> > > > uint32_t *write_msk,
> > > > - enum reg_type type)
> > > > + enum reg_type type,
> > > > + bool bi)
> > > > {
> > > > int caps = 0;
> > > >
> > > > @@ -320,7 +430,7 @@ void cxl_component_register_init_common(uint32_t *reg_state,
> > > > case CXL2_LOGICAL_DEVICE:
> > > > /* + HDM */
> > > > init_cap_reg(HDM, 5, 1);
> > > > - hdm_init_common(reg_state, write_msk, type);
> > > > + hdm_init_common(reg_state, write_msk, type, bi);
> > > > /* fallthrough */
> > > > case CXL2_DOWNSTREAM_PORT:
> > > > case CXL2_DEVICE:
> > > > @@ -335,6 +445,24 @@ void cxl_component_register_init_common(uint32_t *reg_state,
> > > > abort();
> > > > }
> > > >
> > > > + /* back invalidate */
> > > > + if (bi) {
> > > > + switch (type) {
> > > > + case CXL2_UPSTREAM_PORT:
> > > > + init_cap_reg(BI_RT, 11, CXL_BI_RT_CAP_VERSION);
> > > > + bi_rt_init_common(reg_state, write_msk);
> > > > + break;
> > > > + case CXL2_ROOT_PORT:
> > > > + case CXL2_DOWNSTREAM_PORT:
> > > > + case CXL2_TYPE3_DEVICE:
> > > > + init_cap_reg(BI_DECODER, 12, CXL_BI_DECODER_CAP_VERSION);
> > > > + bi_decoder_init_common(reg_state, write_msk, type);
> > > > + break;
> > > > + default:
> > > > + break;
> > > > + }
> > > > + }
> > > > +
> > > > ARRAY_FIELD_DP32(reg_state, CXL_CAPABILITY_HEADER, ARRAY_SIZE, caps);
> > > > #undef init_cap_reg
> > > > }
> > > > diff --git a/hw/mem/cxl_type3.c b/hw/mem/cxl_type3.c
> > > > index 3c7ecd8c48bc..3f09c589ae58 100644
> > > > --- a/hw/mem/cxl_type3.c
> > > > +++ b/hw/mem/cxl_type3.c
> > > > @@ -748,6 +748,11 @@ static bool cxl_setup_memory(CXLType3Dev *ct3d, Error **errp)
> > > > return false;
> > > > }
> > > >
> > > > + if (!ct3d->flitmode && ct3d->hdmdb) {
> > > > + error_setg(errp, "hdm-db requires operating in 256b flit");
> > > > + return false;
> > > > + }
> > > > +
> > > > if (ct3d->hostvmem) {
> > > > MemoryRegion *vmr;
> > > > char *v_name;
> > > > @@ -1317,7 +1322,8 @@ static void ct3d_reset(DeviceState *dev)
> > > >
> > > > pcie_cap_fill_link_ep_usp(PCI_DEVICE(dev), ct3d->width, ct3d->speed,
> > > > ct3d->flitmode);
> > > > - cxl_component_register_init_common(reg_state, write_msk, CXL2_TYPE3_DEVICE);
> > > > + cxl_component_register_init_common(reg_state, write_msk,
> > > > + CXL2_TYPE3_DEVICE, ct3d->hdmdb);
> > > > cxl_device_register_init_t3(ct3d, CXL_T3_MSIX_MBOX);
> > > >
> > > > /*
> > > > @@ -1356,6 +1362,7 @@ static const Property ct3_props[] = {
> > > > DEFINE_PROP_PCIE_LINK_WIDTH("x-width", CXLType3Dev,
> > > > width, PCIE_LINK_WIDTH_16),
> > > > DEFINE_PROP_BOOL("x-256b-flit", CXLType3Dev, flitmode, false),
> > > > + DEFINE_PROP_BOOL("hdm-db", CXLType3Dev, hdmdb, false),
> > > > };
> > > >
> > > > static uint64_t get_lsa_size(CXLType3Dev *ct3d)
> > > > diff --git a/hw/pci-bridge/cxl_downstream.c b/hw/pci-bridge/cxl_downstream.c
> > > > index 64086d8ec2f2..320818a8f1ce 100644
> > > > --- a/hw/pci-bridge/cxl_downstream.c
> > > > +++ b/hw/pci-bridge/cxl_downstream.c
> > > > @@ -39,7 +39,7 @@ static void latch_registers(CXLDownstreamPort *dsp)
> > > > uint32_t *write_msk = dsp->cxl_cstate.crb.cache_mem_regs_write_mask;
> > > >
> > > > cxl_component_register_init_common(reg_state, write_msk,
> > > > - CXL2_DOWNSTREAM_PORT);
> > > > + CXL2_DOWNSTREAM_PORT, true);
> > > > }
> > > >
> > > > /* TODO: Look at sharing this code across all CXL port types */
> > > > diff --git a/hw/pci-bridge/cxl_root_port.c b/hw/pci-bridge/cxl_root_port.c
> > > > index 5641048084a4..e2093ac39ee6 100644
> > > > --- a/hw/pci-bridge/cxl_root_port.c
> > > > +++ b/hw/pci-bridge/cxl_root_port.c
> > > > @@ -101,7 +101,8 @@ static void latch_registers(CXLRootPort *crp)
> > > > uint32_t *reg_state = crp->cxl_cstate.crb.cache_mem_registers;
> > > > uint32_t *write_msk = crp->cxl_cstate.crb.cache_mem_regs_write_mask;
> > > >
> > > > - cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT);
> > > > + cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT,
> > > > + true);
> > > > }
> > > >
> > > > static void build_dvsecs(PCIDevice *d, CXLComponentState *cxl)
> > > > diff --git a/hw/pci-bridge/cxl_upstream.c b/hw/pci-bridge/cxl_upstream.c
> > > > index c352d11dc7b7..fb8d19539c9f 100644
> > > > --- a/hw/pci-bridge/cxl_upstream.c
> > > > +++ b/hw/pci-bridge/cxl_upstream.c
> > > > @@ -90,7 +90,7 @@ static void latch_registers(CXLUpstreamPort *usp)
> > > > uint32_t *write_msk = usp->cxl_cstate.crb.cache_mem_regs_write_mask;
> > > >
> > > > cxl_component_register_init_common(reg_state, write_msk,
> > > > - CXL2_UPSTREAM_PORT);
> > > > + CXL2_UPSTREAM_PORT, usp->flitmode);
> > > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, TARGET_COUNT, 8);
> > > > }
> > > >
> > > > diff --git a/hw/pci-bridge/pci_expander_bridge.c b/hw/pci-bridge/pci_expander_bridge.c
> > > > index b6e2eb796951..11623a5666f6 100644
> > > > --- a/hw/pci-bridge/pci_expander_bridge.c
> > > > +++ b/hw/pci-bridge/pci_expander_bridge.c
> > > > @@ -300,7 +300,7 @@ static void pxb_cxl_dev_reset(DeviceState *dev)
> > > > uint32_t *write_msk = cxl_cstate->crb.cache_mem_regs_write_mask;
> > > > int dsp_count = 0;
> > > >
> > > > - cxl_component_register_init_common(reg_state, write_msk, CXL2_RC);
> > > > + cxl_component_register_init_common(reg_state, write_msk, CXL2_RC, false);
> > > > /*
> > > > * The CXL specification allows for host bridges with no HDM decoders
> > > > * if they only have a single root port.
> > > > --
> > > > 2.51.0
> >
> >
>
>
^ permalink raw reply [flat|nested] 14+ messages in thread* Re: [PATCH qemu v6 6/7] hw/cxl: Support type3 HDM-DB
2026-02-04 15:40 ` Jonathan Cameron
@ 2026-02-04 15:50 ` Jonathan Cameron
0 siblings, 0 replies; 14+ messages in thread
From: Jonathan Cameron @ 2026-02-04 15:50 UTC (permalink / raw)
To: Jonathan Cameron via qemu development, linuxarm
Cc: Michael S. Tsirkin, Davidlohr Bueso, linux-cxl, Ravi Shankar,
Marcel Apfelbaum, Markus Armbruster, Michael Roth
On Wed, 4 Feb 2026 15:40:36 +0000
Jonathan Cameron <jonathan.cameron@huawei.com> wrote:
> On Wed, 4 Feb 2026 15:21:02 +0000
> Jonathan Cameron via qemu development <qemu-devel@nongnu.org> wrote:
>
> > On Wed, 4 Feb 2026 08:44:42 -0500
> > "Michael S. Tsirkin" <mst@redhat.com> wrote:
> >
> > > On Wed, Feb 04, 2026 at 08:24:55AM -0500, Michael S. Tsirkin wrote:
> > > > On Wed, Feb 04, 2026 at 12:12:14PM +0000, Jonathan Cameron wrote:
> > > > > From: Davidlohr Bueso <dave@stgolabs.net>
> > > > >
> > > > > Add basic plumbing for memory expander devices that support Back
> > > > > Invalidation. This introduces a 'hdm-db=on|off' parameter and
> > > > > exposes the relevant BI RT/Decoder component cachemem registers.
> > > > >
> > > > > Some noteworthy properties:
> > > > > - Devices require enabling Flit mode across the CXL topology.
> > > > > - Explicit BI-ID commit is required.
> > > > > - HDM decoder support both host and dev coherency models.
> > > > >
> > > > > Tested-by: Dongjoo Seo <dongjoo.seo1@samsung.com>
> > > > > Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
> > > > > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > > >
> > > > more troubles:
> > > > https://gitlab.com/mstredhat/qemu/-/jobs/12984846000
> > >
> > >
> > > clang just as unhappy:
> > >
> > > https://gitlab.com/mstredhat/qemu/-/jobs/12984846060
> > They both seem to be clang.
> >
> > Replicated.
> >
> > Ah. This old gotcha - at one point I got one of my compiler colleagues to report
> > it as a clang bug but he lost the argument vs the spec. Though I believe
> > it is being fixed in the C spec longer term. I can't find the thread
> > now but we did discuss adding local scope in the macro a while back.
Did some archaeology
https://lore.kernel.org/qemu-devel/20231019124819.00005f6a@Huawei.com/
Can't add scope inside the macro as it's sometimes called outside
of functions. So it's a case of paper over this whenever we happen to hit
it.
Jonathan
> >
> > Anyhow work around is to add scope to avoid label for the case statement
> > being followed by _Static_assert()
> > Despite smelling like a function, it's not and has special rules...
> >
> > Would you like a v7 or squash the following in?
>
> Or. The problem only actually occurs after the next patch (which happens
> to bring the _static assert to the top of the case statement.)
> So drop patch 7 and I'll revisit just that little one at a later date.
>
> > Thanks
> >
> > Jonathan
> >
> >
> > diff --git a/hw/cxl/cxl-component-utils.c b/hw/cxl/cxl-component-utils.c
> > index a3077184e230..07aabe331c44 100644
> > --- a/hw/cxl/cxl-component-utils.c
> > +++ b/hw/cxl/cxl-component-utils.c
> > @@ -68,7 +68,7 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
> > ComponentRegisters *cregs = &cxl_cstate->crb;
> >
> > switch (size) {
> > - case 4:
> > + case 4: {
> > QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
> >
> > if (offset == A_CXL_BI_RT_STATUS ||
> > @@ -101,6 +101,7 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
> > }
> >
> > return cregs->cache_mem_registers[offset / 4];
> > + }
> > case 8:
> > qemu_log_mask(LOG_UNIMP,
> > "CXL 8 byte cache mem registers not implemented\n");
> >
> >
> > >
> > > >
> > > > > ---
> > > > > v6: Initialize type variable to avoid a false compiler warning
> > > > > from some versions of gcc. (Michael Tsirkin)
> > > > > ---
> > > > > docs/system/devices/cxl.rst | 23 +++++
> > > > > include/hw/cxl/cxl_component.h | 54 ++++++++++-
> > > > > include/hw/cxl/cxl_device.h | 3 +
> > > > > hw/cxl/cxl-component-utils.c | 142 ++++++++++++++++++++++++++--
> > > > > hw/mem/cxl_type3.c | 9 +-
> > > > > hw/pci-bridge/cxl_downstream.c | 2 +-
> > > > > hw/pci-bridge/cxl_root_port.c | 3 +-
> > > > > hw/pci-bridge/cxl_upstream.c | 2 +-
> > > > > hw/pci-bridge/pci_expander_bridge.c | 2 +-
> > > > > 9 files changed, 225 insertions(+), 15 deletions(-)
> > > > >
> > > > > diff --git a/docs/system/devices/cxl.rst b/docs/system/devices/cxl.rst
> > > > > index ca15a0da1c1d..9d0771cdfd73 100644
> > > > > --- a/docs/system/devices/cxl.rst
> > > > > +++ b/docs/system/devices/cxl.rst
> > > > > @@ -384,6 +384,29 @@ An example of 4 devices below a switch suitable for 1, 2 or 4 way interleave::
> > > > > -device cxl-type3,bus=swport3,persistent-memdev=cxl-mem3,lsa=cxl-lsa3,id=cxl-pmem3,sn=0x4 \
> > > > > -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
> > > > >
> > > > > +An example of 4 type3 devices with volatile memory below a switch. Two of the devices
> > > > > +use HDM-DB for coherence, which requires operating in Flit mode::
> > > > > +
> > > > > + qemu-system-x86_64 -M q35,cxl=on -m 4G,maxmem=8G,slots=8 -smp 4 \
> > > > > + ...
> > > > > + -object memory-backend-ram,id=cxl-mem0,share=on,size=256M \
> > > > > + -object memory-backend-ram,id=cxl-mem1,share=on,size=256M \
> > > > > + -object memory-backend-ram,id=cxl-mem2,share=on,size=256M \
> > > > > + -object memory-backend-ram,id=cxl-mem3,share=on,size=256M \
> > > > > + -device pxb-cxl,bus_nr=12,bus=pcie.0,id=cxl.1 \
> > > > > + -device cxl-rp,port=0,bus=cxl.1,id=root_port0,chassis=0,slot=0 \
> > > > > + -device cxl-rp,port=1,bus=cxl.1,id=root_port1,chassis=0,slot=1 \
> > > > > + -device cxl-upstream,bus=root_port0,id=us0,x-256b-flit=on \
> > > > > + -device cxl-downstream,port=0,bus=us0,id=swport0,chassis=0,slot=4 \
> > > > > + -device cxl-type3,bus=swport0,volatile-memdev=cxl-mem0,id=cxl-mem0,sn=0x1,x-256b-flit=on,hdm-db=on \
> > > > > + -device cxl-downstream,port=1,bus=us0,id=swport1,chassis=0,slot=5 \
> > > > > + -device cxl-type3,bus=swport1,volatile-memdev=cxl-mem1,id=cxl-mem1,sn=0x2,x-256b-flit=on,hdm-db=on \
> > > > > + -device cxl-downstream,port=2,bus=us0,id=swport2,chassis=0,slot=6 \
> > > > > + -device cxl-type3,bus=swport2,volatile-memdev=cxl-mem2,id=cxl-mem2,sn=0x3 \
> > > > > + -device cxl-downstream,port=3,bus=us0,id=swport3,chassis=0,slot=7 \
> > > > > + -device cxl-type3,bus=swport3,volatile-memdev=cxl-mem3,id=cxl-mem3,sn=0x4 \
> > > > > + -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
> > > > > +
> > > > > A simple arm/virt example featuring a single direct connected CXL Type 3
> > > > > Volatile Memory device::
> > > > >
> > > > > diff --git a/include/hw/cxl/cxl_component.h b/include/hw/cxl/cxl_component.h
> > > > > index 1f167d3ef79b..ffc82202206c 100644
> > > > > --- a/include/hw/cxl/cxl_component.h
> > > > > +++ b/include/hw/cxl/cxl_component.h
> > > > > @@ -67,6 +67,8 @@ CXLx_CAPABILITY_HEADER(LINK, 2)
> > > > > CXLx_CAPABILITY_HEADER(HDM, 3)
> > > > > CXLx_CAPABILITY_HEADER(EXTSEC, 4)
> > > > > CXLx_CAPABILITY_HEADER(SNOOP, 5)
> > > > > +CXLx_CAPABILITY_HEADER(BI_RT, 6)
> > > > > +CXLx_CAPABILITY_HEADER(BI_DECODER, 7)
> > > > >
> > > > > /*
> > > > > * Capability structures contain the actual registers that the CXL component
> > > > > @@ -211,10 +213,55 @@ HDM_DECODER_INIT(3);
> > > > > (CXL_IDE_REGISTERS_OFFSET + CXL_IDE_REGISTERS_SIZE)
> > > > > #define CXL_SNOOP_REGISTERS_SIZE 0x8
> > > > >
> > > > > -QEMU_BUILD_BUG_MSG((CXL_SNOOP_REGISTERS_OFFSET +
> > > > > - CXL_SNOOP_REGISTERS_SIZE) >= 0x1000,
> > > > > +#define CXL_BI_RT_CAP_VERSION 1
> > > > > +#define CXL_BI_RT_REGISTERS_OFFSET \
> > > > > + (CXL_SNOOP_REGISTERS_OFFSET + CXL_SNOOP_REGISTERS_SIZE)
> > > > > +#define CXL_BI_RT_REGISTERS_SIZE 0xC
> > > > > +
> > > > > +REG32(CXL_BI_RT_CAPABILITY, CXL_BI_RT_REGISTERS_OFFSET)
> > > > > + FIELD(CXL_BI_RT_CAPABILITY, EXPLICIT_COMMIT, 0, 1)
> > > > > +REG32(CXL_BI_RT_CTRL, CXL_BI_RT_REGISTERS_OFFSET + 0x4)
> > > > > + FIELD(CXL_BI_RT_CTRL, COMMIT, 0, 1)
> > > > > +REG32(CXL_BI_RT_STATUS, CXL_BI_RT_REGISTERS_OFFSET + 0x8)
> > > > > + FIELD(CXL_BI_RT_STATUS, COMMITTED, 0, 1)
> > > > > + FIELD(CXL_BI_RT_STATUS, ERR_NOT_COMMITTED, 1, 1)
> > > > > + FIELD(CXL_BI_RT_STATUS, COMMIT_TMO_SCALE, 8, 4)
> > > > > + FIELD(CXL_BI_RT_STATUS, COMMIT_TMO_BASE, 12, 4)
> > > > > +
> > > > > +/* CXL r3.2 8.2.4.27 - CXL BI Decoder Capability Structure */
> > > > > +#define CXL_BI_DECODER_CAP_VERSION 1
> > > > > +#define CXL_BI_DECODER_REGISTERS_OFFSET \
> > > > > + (CXL_BI_RT_REGISTERS_OFFSET + CXL_BI_RT_REGISTERS_SIZE)
> > > > > +#define CXL_BI_DECODER_REGISTERS_SIZE 0xC
> > > > > +
> > > > > +REG32(CXL_BI_DECODER_CAPABILITY, CXL_BI_DECODER_REGISTERS_OFFSET)
> > > > > + FIELD(CXL_BI_DECODER_CAPABILITY, HDM_D, 0, 1)
> > > > > + FIELD(CXL_BI_DECODER_CAPABILITY, EXPLICIT_COMMIT, 1, 1)
> > > > > +REG32(CXL_BI_DECODER_CTRL, CXL_BI_DECODER_REGISTERS_OFFSET + 0x4)
> > > > > + FIELD(CXL_BI_DECODER_CTRL, BI_FW, 0, 1)
> > > > > + FIELD(CXL_BI_DECODER_CTRL, BI_ENABLE, 1, 1)
> > > > > + FIELD(CXL_BI_DECODER_CTRL, COMMIT, 2, 1)
> > > > > +REG32(CXL_BI_DECODER_STATUS, CXL_BI_DECODER_REGISTERS_OFFSET + 0x8)
> > > > > + FIELD(CXL_BI_DECODER_STATUS, COMMITTED, 0, 1)
> > > > > + FIELD(CXL_BI_DECODER_STATUS, ERR_NOT_COMMITTED, 1, 1)
> > > > > + FIELD(CXL_BI_DECODER_STATUS, COMMIT_TMO_SCALE, 8, 4)
> > > > > + FIELD(CXL_BI_DECODER_STATUS, COMMIT_TMO_BASE, 12, 4)
> > > > > +
> > > > > +QEMU_BUILD_BUG_MSG((CXL_BI_DECODER_REGISTERS_OFFSET +
> > > > > + CXL_BI_DECODER_REGISTERS_SIZE) >= 0x1000,
> > > > > "No space for registers");
> > > > >
> > > > > +/* track BI explicit commit handling for route table and decoder */
> > > > > +enum {
> > > > > + CXL_BISTATE_RT = 0,
> > > > > + CXL_BISTATE_DECODER,
> > > > > + CXL_BISTATE_MAX
> > > > > +};
> > > > > +
> > > > > +typedef struct bi_state {
> > > > > + uint64_t last_commit; /* last 0->1 transition */
> > > > > +} BIState;
> > > > > +
> > > > > typedef struct component_registers {
> > > > > /*
> > > > > * Main memory region to be registered with QEMU core.
> > > > > @@ -259,6 +306,7 @@ typedef struct cxl_component {
> > > > > };
> > > > >
> > > > > CDATObject cdat;
> > > > > + BIState bi_state[CXL_BISTATE_MAX];
> > > > > } CXLComponentState;
> > > > >
> > > > > void cxl_component_register_block_init(Object *obj,
> > > > > @@ -266,7 +314,7 @@ void cxl_component_register_block_init(Object *obj,
> > > > > const char *type);
> > > > > void cxl_component_register_init_common(uint32_t *reg_state,
> > > > > uint32_t *write_msk,
> > > > > - enum reg_type type);
> > > > > + enum reg_type type, bool bi);
> > > > >
> > > > > void cxl_component_create_dvsec(CXLComponentState *cxl_cstate,
> > > > > enum reg_type cxl_dev_type, uint16_t length,
> > > > > diff --git a/include/hw/cxl/cxl_device.h b/include/hw/cxl/cxl_device.h
> > > > > index 7d9236db8c85..393f3122173b 100644
> > > > > --- a/include/hw/cxl/cxl_device.h
> > > > > +++ b/include/hw/cxl/cxl_device.h
> > > > > @@ -770,6 +770,9 @@ struct CXLType3Dev {
> > > > > CXLMemSparingReadAttrs rank_sparing_attrs;
> > > > > CXLMemSparingWriteAttrs rank_sparing_wr_attrs;
> > > > >
> > > > > + /* BI flows */
> > > > > + bool hdmdb;
> > > > > +
> > > > > struct dynamic_capacity {
> > > > > HostMemoryBackend *host_dc;
> > > > > AddressSpace host_dc_as;
> > > > > diff --git a/hw/cxl/cxl-component-utils.c b/hw/cxl/cxl-component-utils.c
> > > > > index 91770f103a85..a7d36e1128c2 100644
> > > > > --- a/hw/cxl/cxl-component-utils.c
> > > > > +++ b/hw/cxl/cxl-component-utils.c
> > > > > @@ -71,10 +71,40 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
> > > > > case 4:
> > > > > if (cregs->special_ops && cregs->special_ops->read) {
> > > > > return cregs->special_ops->read(cxl_cstate, offset, 4);
> > > > > - } else {
> > > > > - QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
> > > > > - return cregs->cache_mem_registers[offset / 4];
> > > > > }
> > > > > +
> > > > > + QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
> > > > > +
> > > > > + if (offset == A_CXL_BI_RT_STATUS ||
> > > > > + offset == A_CXL_BI_DECODER_STATUS) {
> > > > > + int type;
> > > > > + uint64_t started;
> > > > > +
> > > > > + type = (offset == A_CXL_BI_RT_STATUS) ?
> > > > > + CXL_BISTATE_RT : CXL_BISTATE_DECODER;
> > > > > + started = cxl_cstate->bi_state[type].last_commit;
> > > > > +
> > > > > + if (started) {
> > > > > + uint32_t *cache_mem = cregs->cache_mem_registers;
> > > > > + uint32_t val = cache_mem[offset / 4];
> > > > > + uint64_t now;
> > > > > + int set;
> > > > > +
> > > > > + now = qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
> > > > > + /* arbitrary 100 ms to do the commit */
> > > > > + set = !!(now >= started + 100);
> > > > > +
> > > > > + if (offset == A_CXL_BI_RT_STATUS) {
> > > > > + val = FIELD_DP32(val, CXL_BI_RT_STATUS, COMMITTED, set);
> > > > > + } else {
> > > > > + val = FIELD_DP32(val, CXL_BI_DECODER_STATUS, COMMITTED,
> > > > > + set);
> > > > > + }
> > > > > + stl_le_p((uint8_t *)cache_mem + offset, val);
> > > > > + }
> > > > > + }
> > > > > +
> > > > > + return cregs->cache_mem_registers[offset / 4];
> > > > > case 8:
> > > > > qemu_log_mask(LOG_UNIMP,
> > > > > "CXL 8 byte cache mem registers not implemented\n");
> > > > > @@ -118,6 +148,47 @@ static void dumb_hdm_handler(CXLComponentState *cxl_cstate, hwaddr offset,
> > > > > stl_le_p((uint8_t *)cache_mem + offset, value);
> > > > > }
> > > > >
> > > > > +static void bi_handler(CXLComponentState *cxl_cstate, hwaddr offset,
> > > > > + uint32_t value)
> > > > > +{
> > > > > + ComponentRegisters *cregs = &cxl_cstate->crb;
> > > > > + uint32_t sts, *cache_mem = cregs->cache_mem_registers;
> > > > > + bool to_commit = false;
> > > > > + int type = 0; /* Unused value - work around for compiler warning */
> > > > > +
> > > > > + switch (offset) {
> > > > > + case A_CXL_BI_RT_CTRL:
> > > > > + to_commit = FIELD_EX32(value, CXL_BI_RT_CTRL, COMMIT);
> > > > > + if (to_commit) {
> > > > > + sts = cxl_cache_mem_read_reg(cxl_cstate,
> > > > > + R_CXL_BI_RT_STATUS, 4);
> > > > > + sts = FIELD_DP32(sts, CXL_BI_RT_STATUS, COMMITTED, 0);
> > > > > + stl_le_p((uint8_t *)cache_mem + R_CXL_BI_RT_STATUS, sts);
> > > > > + type = CXL_BISTATE_RT;
> > > > > + }
> > > > > + break;
> > > > > + case A_CXL_BI_DECODER_CTRL:
> > > > > + to_commit = FIELD_EX32(value, CXL_BI_DECODER_CTRL, COMMIT);
> > > > > + if (to_commit) {
> > > > > + sts = cxl_cache_mem_read_reg(cxl_cstate,
> > > > > + R_CXL_BI_DECODER_STATUS, 4);
> > > > > + sts = FIELD_DP32(sts, CXL_BI_DECODER_STATUS, COMMITTED, 0);
> > > > > + stl_le_p((uint8_t *)cache_mem + R_CXL_BI_DECODER_STATUS, sts);
> > > > > + type = CXL_BISTATE_DECODER;
> > > > > + }
> > > > > + break;
> > > > > + default:
> > > > > + break;
> > > > > + }
> > > > > +
> > > > > + if (to_commit) {
> > > > > + cxl_cstate->bi_state[type].last_commit =
> > > > > + qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
> > > > > + }
> > > > > +
> > > > > + stl_le_p((uint8_t *)cache_mem + offset, value);
> > > > > +}
> > > > > +
> > > > > static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
> > > > > unsigned size)
> > > > > {
> > > > > @@ -141,6 +212,9 @@ static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
> > > > > if (offset >= A_CXL_HDM_DECODER_CAPABILITY &&
> > > > > offset <= A_CXL_HDM_DECODER3_TARGET_LIST_HI) {
> > > > > dumb_hdm_handler(cxl_cstate, offset, value);
> > > > > + } else if (offset == A_CXL_BI_RT_CTRL ||
> > > > > + offset == A_CXL_BI_DECODER_CTRL) {
> > > > > + bi_handler(cxl_cstate, offset, value);
> > > > > } else {
> > > > > cregs->cache_mem_registers[offset / 4] = value;
> > > > > }
> > > > > @@ -230,7 +304,7 @@ static void ras_init_common(uint32_t *reg_state, uint32_t *write_msk)
> > > > > }
> > > > >
> > > > > static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > > > - enum reg_type type)
> > > > > + enum reg_type type, bool bi)
> > > > > {
> > > > > int decoder_count = CXL_HDM_DECODER_COUNT;
> > > > > int hdm_inc = R_CXL_HDM_DECODER1_BASE_LO - R_CXL_HDM_DECODER0_BASE_LO;
> > > > > @@ -255,7 +329,9 @@ static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > > > UIO_DECODER_COUNT, 0);
> > > > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, MEMDATA_NXM_CAP, 0);
> > > > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY,
> > > > > - SUPPORTED_COHERENCY_MODEL, 0); /* Unknown */
> > > > > + SUPPORTED_COHERENCY_MODEL,
> > > > > + /* host+dev or Unknown */
> > > > > + type == CXL2_TYPE3_DEVICE && bi ? 3 : 0);
> > > > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_GLOBAL_CONTROL,
> > > > > HDM_DECODER_ENABLE, 0);
> > > > > write_msk[R_CXL_HDM_DECODER_GLOBAL_CONTROL] = 0x3;
> > > > > @@ -278,9 +354,43 @@ static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > > > }
> > > > > }
> > > > >
> > > > > +static void bi_rt_init_common(uint32_t *reg_state, uint32_t *write_msk)
> > > > > +{
> > > > > + /* switch usp must commit the new BI-ID, timeout of 2secs */
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_CAPABILITY, EXPLICIT_COMMIT, 1);
> > > > > +
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_CTRL, COMMIT, 0);
> > > > > + write_msk[R_CXL_BI_RT_CTRL] = 0x1;
> > > > > +
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMITTED, 0);
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, ERR_NOT_COMMITTED, 0);
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMIT_TMO_SCALE, 0x6);
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMIT_TMO_BASE, 0x2);
> > > > > +}
> > > > > +
> > > > > +static void bi_decoder_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > > > + enum reg_type type)
> > > > > +{
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CAPABILITY, HDM_D, 0);
> > > > > + /* switch dsp must commit the new BI-ID, timeout of 2secs */
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CAPABILITY, EXPLICIT_COMMIT,
> > > > > + (type != CXL2_ROOT_PORT && type != CXL2_TYPE3_DEVICE));
> > > > > +
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, BI_FW, 0);
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, BI_ENABLE, 0);
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, COMMIT, 0);
> > > > > + write_msk[R_CXL_BI_DECODER_CTRL] = 0x7;
> > > > > +
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMITTED, 0);
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, ERR_NOT_COMMITTED, 0);
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMIT_TMO_SCALE, 0x6);
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMIT_TMO_BASE, 0x2);
> > > > > +}
> > > > > +
> > > > > void cxl_component_register_init_common(uint32_t *reg_state,
> > > > > uint32_t *write_msk,
> > > > > - enum reg_type type)
> > > > > + enum reg_type type,
> > > > > + bool bi)
> > > > > {
> > > > > int caps = 0;
> > > > >
> > > > > @@ -320,7 +430,7 @@ void cxl_component_register_init_common(uint32_t *reg_state,
> > > > > case CXL2_LOGICAL_DEVICE:
> > > > > /* + HDM */
> > > > > init_cap_reg(HDM, 5, 1);
> > > > > - hdm_init_common(reg_state, write_msk, type);
> > > > > + hdm_init_common(reg_state, write_msk, type, bi);
> > > > > /* fallthrough */
> > > > > case CXL2_DOWNSTREAM_PORT:
> > > > > case CXL2_DEVICE:
> > > > > @@ -335,6 +445,24 @@ void cxl_component_register_init_common(uint32_t *reg_state,
> > > > > abort();
> > > > > }
> > > > >
> > > > > + /* back invalidate */
> > > > > + if (bi) {
> > > > > + switch (type) {
> > > > > + case CXL2_UPSTREAM_PORT:
> > > > > + init_cap_reg(BI_RT, 11, CXL_BI_RT_CAP_VERSION);
> > > > > + bi_rt_init_common(reg_state, write_msk);
> > > > > + break;
> > > > > + case CXL2_ROOT_PORT:
> > > > > + case CXL2_DOWNSTREAM_PORT:
> > > > > + case CXL2_TYPE3_DEVICE:
> > > > > + init_cap_reg(BI_DECODER, 12, CXL_BI_DECODER_CAP_VERSION);
> > > > > + bi_decoder_init_common(reg_state, write_msk, type);
> > > > > + break;
> > > > > + default:
> > > > > + break;
> > > > > + }
> > > > > + }
> > > > > +
> > > > > ARRAY_FIELD_DP32(reg_state, CXL_CAPABILITY_HEADER, ARRAY_SIZE, caps);
> > > > > #undef init_cap_reg
> > > > > }
> > > > > diff --git a/hw/mem/cxl_type3.c b/hw/mem/cxl_type3.c
> > > > > index 3c7ecd8c48bc..3f09c589ae58 100644
> > > > > --- a/hw/mem/cxl_type3.c
> > > > > +++ b/hw/mem/cxl_type3.c
> > > > > @@ -748,6 +748,11 @@ static bool cxl_setup_memory(CXLType3Dev *ct3d, Error **errp)
> > > > > return false;
> > > > > }
> > > > >
> > > > > + if (!ct3d->flitmode && ct3d->hdmdb) {
> > > > > + error_setg(errp, "hdm-db requires operating in 256b flit");
> > > > > + return false;
> > > > > + }
> > > > > +
> > > > > if (ct3d->hostvmem) {
> > > > > MemoryRegion *vmr;
> > > > > char *v_name;
> > > > > @@ -1317,7 +1322,8 @@ static void ct3d_reset(DeviceState *dev)
> > > > >
> > > > > pcie_cap_fill_link_ep_usp(PCI_DEVICE(dev), ct3d->width, ct3d->speed,
> > > > > ct3d->flitmode);
> > > > > - cxl_component_register_init_common(reg_state, write_msk, CXL2_TYPE3_DEVICE);
> > > > > + cxl_component_register_init_common(reg_state, write_msk,
> > > > > + CXL2_TYPE3_DEVICE, ct3d->hdmdb);
> > > > > cxl_device_register_init_t3(ct3d, CXL_T3_MSIX_MBOX);
> > > > >
> > > > > /*
> > > > > @@ -1356,6 +1362,7 @@ static const Property ct3_props[] = {
> > > > > DEFINE_PROP_PCIE_LINK_WIDTH("x-width", CXLType3Dev,
> > > > > width, PCIE_LINK_WIDTH_16),
> > > > > DEFINE_PROP_BOOL("x-256b-flit", CXLType3Dev, flitmode, false),
> > > > > + DEFINE_PROP_BOOL("hdm-db", CXLType3Dev, hdmdb, false),
> > > > > };
> > > > >
> > > > > static uint64_t get_lsa_size(CXLType3Dev *ct3d)
> > > > > diff --git a/hw/pci-bridge/cxl_downstream.c b/hw/pci-bridge/cxl_downstream.c
> > > > > index 64086d8ec2f2..320818a8f1ce 100644
> > > > > --- a/hw/pci-bridge/cxl_downstream.c
> > > > > +++ b/hw/pci-bridge/cxl_downstream.c
> > > > > @@ -39,7 +39,7 @@ static void latch_registers(CXLDownstreamPort *dsp)
> > > > > uint32_t *write_msk = dsp->cxl_cstate.crb.cache_mem_regs_write_mask;
> > > > >
> > > > > cxl_component_register_init_common(reg_state, write_msk,
> > > > > - CXL2_DOWNSTREAM_PORT);
> > > > > + CXL2_DOWNSTREAM_PORT, true);
> > > > > }
> > > > >
> > > > > /* TODO: Look at sharing this code across all CXL port types */
> > > > > diff --git a/hw/pci-bridge/cxl_root_port.c b/hw/pci-bridge/cxl_root_port.c
> > > > > index 5641048084a4..e2093ac39ee6 100644
> > > > > --- a/hw/pci-bridge/cxl_root_port.c
> > > > > +++ b/hw/pci-bridge/cxl_root_port.c
> > > > > @@ -101,7 +101,8 @@ static void latch_registers(CXLRootPort *crp)
> > > > > uint32_t *reg_state = crp->cxl_cstate.crb.cache_mem_registers;
> > > > > uint32_t *write_msk = crp->cxl_cstate.crb.cache_mem_regs_write_mask;
> > > > >
> > > > > - cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT);
> > > > > + cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT,
> > > > > + true);
> > > > > }
> > > > >
> > > > > static void build_dvsecs(PCIDevice *d, CXLComponentState *cxl)
> > > > > diff --git a/hw/pci-bridge/cxl_upstream.c b/hw/pci-bridge/cxl_upstream.c
> > > > > index c352d11dc7b7..fb8d19539c9f 100644
> > > > > --- a/hw/pci-bridge/cxl_upstream.c
> > > > > +++ b/hw/pci-bridge/cxl_upstream.c
> > > > > @@ -90,7 +90,7 @@ static void latch_registers(CXLUpstreamPort *usp)
> > > > > uint32_t *write_msk = usp->cxl_cstate.crb.cache_mem_regs_write_mask;
> > > > >
> > > > > cxl_component_register_init_common(reg_state, write_msk,
> > > > > - CXL2_UPSTREAM_PORT);
> > > > > + CXL2_UPSTREAM_PORT, usp->flitmode);
> > > > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, TARGET_COUNT, 8);
> > > > > }
> > > > >
> > > > > diff --git a/hw/pci-bridge/pci_expander_bridge.c b/hw/pci-bridge/pci_expander_bridge.c
> > > > > index b6e2eb796951..11623a5666f6 100644
> > > > > --- a/hw/pci-bridge/pci_expander_bridge.c
> > > > > +++ b/hw/pci-bridge/pci_expander_bridge.c
> > > > > @@ -300,7 +300,7 @@ static void pxb_cxl_dev_reset(DeviceState *dev)
> > > > > uint32_t *write_msk = cxl_cstate->crb.cache_mem_regs_write_mask;
> > > > > int dsp_count = 0;
> > > > >
> > > > > - cxl_component_register_init_common(reg_state, write_msk, CXL2_RC);
> > > > > + cxl_component_register_init_common(reg_state, write_msk, CXL2_RC, false);
> > > > > /*
> > > > > * The CXL specification allows for host bridges with no HDM decoders
> > > > > * if they only have a single root port.
> > > > > --
> > > > > 2.51.0
> > >
> > >
> >
> >
>
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH qemu v6 6/7] hw/cxl: Support type3 HDM-DB
2026-02-04 15:21 ` Jonathan Cameron
2026-02-04 15:40 ` Jonathan Cameron
@ 2026-02-04 16:48 ` Michael S. Tsirkin
1 sibling, 0 replies; 14+ messages in thread
From: Michael S. Tsirkin @ 2026-02-04 16:48 UTC (permalink / raw)
To: Jonathan Cameron
Cc: qemu-devel, Davidlohr Bueso, linuxarm, linux-cxl, Ravi Shankar,
Marcel Apfelbaum, Markus Armbruster, Michael Roth
On Wed, Feb 04, 2026 at 03:21:02PM +0000, Jonathan Cameron wrote:
> On Wed, 4 Feb 2026 08:44:42 -0500
> "Michael S. Tsirkin" <mst@redhat.com> wrote:
>
> > On Wed, Feb 04, 2026 at 08:24:55AM -0500, Michael S. Tsirkin wrote:
> > > On Wed, Feb 04, 2026 at 12:12:14PM +0000, Jonathan Cameron wrote:
> > > > From: Davidlohr Bueso <dave@stgolabs.net>
> > > >
> > > > Add basic plumbing for memory expander devices that support Back
> > > > Invalidation. This introduces a 'hdm-db=on|off' parameter and
> > > > exposes the relevant BI RT/Decoder component cachemem registers.
> > > >
> > > > Some noteworthy properties:
> > > > - Devices require enabling Flit mode across the CXL topology.
> > > > - Explicit BI-ID commit is required.
> > > > - HDM decoder support both host and dev coherency models.
> > > >
> > > > Tested-by: Dongjoo Seo <dongjoo.seo1@samsung.com>
> > > > Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
> > > > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > >
> > > more troubles:
> > > https://gitlab.com/mstredhat/qemu/-/jobs/12984846000
> >
> >
> > clang just as unhappy:
> >
> > https://gitlab.com/mstredhat/qemu/-/jobs/12984846060
> They both seem to be clang.
>
> Replicated.
>
> Ah. This old gotcha - at one point I got one of my compiler colleagues to report
> it as a clang bug but he lost the argument vs the spec. Though I believe
> it is being fixed in the C spec longer term.
Yes the compiler actually says it's been fixed in C23.
> I can't find the thread
> now but we did discuss adding local scope in the macro a while back.
>
> Anyhow work around is to add scope to avoid label for the case statement
> being followed by _Static_assert()
> Despite smelling like a function, it's not and has special rules...
>
> Would you like a v7 or squash the following in?
> Thanks
>
> Jonathan
v7 pls.
>
> diff --git a/hw/cxl/cxl-component-utils.c b/hw/cxl/cxl-component-utils.c
> index a3077184e230..07aabe331c44 100644
> --- a/hw/cxl/cxl-component-utils.c
> +++ b/hw/cxl/cxl-component-utils.c
> @@ -68,7 +68,7 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
> ComponentRegisters *cregs = &cxl_cstate->crb;
>
> switch (size) {
> - case 4:
> + case 4: {
> QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
>
> if (offset == A_CXL_BI_RT_STATUS ||
> @@ -101,6 +101,7 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
> }
>
> return cregs->cache_mem_registers[offset / 4];
> + }
> case 8:
> qemu_log_mask(LOG_UNIMP,
> "CXL 8 byte cache mem registers not implemented\n");
>
>
> >
> > >
> > > > ---
> > > > v6: Initialize type variable to avoid a false compiler warning
> > > > from some versions of gcc. (Michael Tsirkin)
> > > > ---
> > > > docs/system/devices/cxl.rst | 23 +++++
> > > > include/hw/cxl/cxl_component.h | 54 ++++++++++-
> > > > include/hw/cxl/cxl_device.h | 3 +
> > > > hw/cxl/cxl-component-utils.c | 142 ++++++++++++++++++++++++++--
> > > > hw/mem/cxl_type3.c | 9 +-
> > > > hw/pci-bridge/cxl_downstream.c | 2 +-
> > > > hw/pci-bridge/cxl_root_port.c | 3 +-
> > > > hw/pci-bridge/cxl_upstream.c | 2 +-
> > > > hw/pci-bridge/pci_expander_bridge.c | 2 +-
> > > > 9 files changed, 225 insertions(+), 15 deletions(-)
> > > >
> > > > diff --git a/docs/system/devices/cxl.rst b/docs/system/devices/cxl.rst
> > > > index ca15a0da1c1d..9d0771cdfd73 100644
> > > > --- a/docs/system/devices/cxl.rst
> > > > +++ b/docs/system/devices/cxl.rst
> > > > @@ -384,6 +384,29 @@ An example of 4 devices below a switch suitable for 1, 2 or 4 way interleave::
> > > > -device cxl-type3,bus=swport3,persistent-memdev=cxl-mem3,lsa=cxl-lsa3,id=cxl-pmem3,sn=0x4 \
> > > > -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
> > > >
> > > > +An example of 4 type3 devices with volatile memory below a switch. Two of the devices
> > > > +use HDM-DB for coherence, which requires operating in Flit mode::
> > > > +
> > > > + qemu-system-x86_64 -M q35,cxl=on -m 4G,maxmem=8G,slots=8 -smp 4 \
> > > > + ...
> > > > + -object memory-backend-ram,id=cxl-mem0,share=on,size=256M \
> > > > + -object memory-backend-ram,id=cxl-mem1,share=on,size=256M \
> > > > + -object memory-backend-ram,id=cxl-mem2,share=on,size=256M \
> > > > + -object memory-backend-ram,id=cxl-mem3,share=on,size=256M \
> > > > + -device pxb-cxl,bus_nr=12,bus=pcie.0,id=cxl.1 \
> > > > + -device cxl-rp,port=0,bus=cxl.1,id=root_port0,chassis=0,slot=0 \
> > > > + -device cxl-rp,port=1,bus=cxl.1,id=root_port1,chassis=0,slot=1 \
> > > > + -device cxl-upstream,bus=root_port0,id=us0,x-256b-flit=on \
> > > > + -device cxl-downstream,port=0,bus=us0,id=swport0,chassis=0,slot=4 \
> > > > + -device cxl-type3,bus=swport0,volatile-memdev=cxl-mem0,id=cxl-mem0,sn=0x1,x-256b-flit=on,hdm-db=on \
> > > > + -device cxl-downstream,port=1,bus=us0,id=swport1,chassis=0,slot=5 \
> > > > + -device cxl-type3,bus=swport1,volatile-memdev=cxl-mem1,id=cxl-mem1,sn=0x2,x-256b-flit=on,hdm-db=on \
> > > > + -device cxl-downstream,port=2,bus=us0,id=swport2,chassis=0,slot=6 \
> > > > + -device cxl-type3,bus=swport2,volatile-memdev=cxl-mem2,id=cxl-mem2,sn=0x3 \
> > > > + -device cxl-downstream,port=3,bus=us0,id=swport3,chassis=0,slot=7 \
> > > > + -device cxl-type3,bus=swport3,volatile-memdev=cxl-mem3,id=cxl-mem3,sn=0x4 \
> > > > + -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
> > > > +
> > > > A simple arm/virt example featuring a single direct connected CXL Type 3
> > > > Volatile Memory device::
> > > >
> > > > diff --git a/include/hw/cxl/cxl_component.h b/include/hw/cxl/cxl_component.h
> > > > index 1f167d3ef79b..ffc82202206c 100644
> > > > --- a/include/hw/cxl/cxl_component.h
> > > > +++ b/include/hw/cxl/cxl_component.h
> > > > @@ -67,6 +67,8 @@ CXLx_CAPABILITY_HEADER(LINK, 2)
> > > > CXLx_CAPABILITY_HEADER(HDM, 3)
> > > > CXLx_CAPABILITY_HEADER(EXTSEC, 4)
> > > > CXLx_CAPABILITY_HEADER(SNOOP, 5)
> > > > +CXLx_CAPABILITY_HEADER(BI_RT, 6)
> > > > +CXLx_CAPABILITY_HEADER(BI_DECODER, 7)
> > > >
> > > > /*
> > > > * Capability structures contain the actual registers that the CXL component
> > > > @@ -211,10 +213,55 @@ HDM_DECODER_INIT(3);
> > > > (CXL_IDE_REGISTERS_OFFSET + CXL_IDE_REGISTERS_SIZE)
> > > > #define CXL_SNOOP_REGISTERS_SIZE 0x8
> > > >
> > > > -QEMU_BUILD_BUG_MSG((CXL_SNOOP_REGISTERS_OFFSET +
> > > > - CXL_SNOOP_REGISTERS_SIZE) >= 0x1000,
> > > > +#define CXL_BI_RT_CAP_VERSION 1
> > > > +#define CXL_BI_RT_REGISTERS_OFFSET \
> > > > + (CXL_SNOOP_REGISTERS_OFFSET + CXL_SNOOP_REGISTERS_SIZE)
> > > > +#define CXL_BI_RT_REGISTERS_SIZE 0xC
> > > > +
> > > > +REG32(CXL_BI_RT_CAPABILITY, CXL_BI_RT_REGISTERS_OFFSET)
> > > > + FIELD(CXL_BI_RT_CAPABILITY, EXPLICIT_COMMIT, 0, 1)
> > > > +REG32(CXL_BI_RT_CTRL, CXL_BI_RT_REGISTERS_OFFSET + 0x4)
> > > > + FIELD(CXL_BI_RT_CTRL, COMMIT, 0, 1)
> > > > +REG32(CXL_BI_RT_STATUS, CXL_BI_RT_REGISTERS_OFFSET + 0x8)
> > > > + FIELD(CXL_BI_RT_STATUS, COMMITTED, 0, 1)
> > > > + FIELD(CXL_BI_RT_STATUS, ERR_NOT_COMMITTED, 1, 1)
> > > > + FIELD(CXL_BI_RT_STATUS, COMMIT_TMO_SCALE, 8, 4)
> > > > + FIELD(CXL_BI_RT_STATUS, COMMIT_TMO_BASE, 12, 4)
> > > > +
> > > > +/* CXL r3.2 8.2.4.27 - CXL BI Decoder Capability Structure */
> > > > +#define CXL_BI_DECODER_CAP_VERSION 1
> > > > +#define CXL_BI_DECODER_REGISTERS_OFFSET \
> > > > + (CXL_BI_RT_REGISTERS_OFFSET + CXL_BI_RT_REGISTERS_SIZE)
> > > > +#define CXL_BI_DECODER_REGISTERS_SIZE 0xC
> > > > +
> > > > +REG32(CXL_BI_DECODER_CAPABILITY, CXL_BI_DECODER_REGISTERS_OFFSET)
> > > > + FIELD(CXL_BI_DECODER_CAPABILITY, HDM_D, 0, 1)
> > > > + FIELD(CXL_BI_DECODER_CAPABILITY, EXPLICIT_COMMIT, 1, 1)
> > > > +REG32(CXL_BI_DECODER_CTRL, CXL_BI_DECODER_REGISTERS_OFFSET + 0x4)
> > > > + FIELD(CXL_BI_DECODER_CTRL, BI_FW, 0, 1)
> > > > + FIELD(CXL_BI_DECODER_CTRL, BI_ENABLE, 1, 1)
> > > > + FIELD(CXL_BI_DECODER_CTRL, COMMIT, 2, 1)
> > > > +REG32(CXL_BI_DECODER_STATUS, CXL_BI_DECODER_REGISTERS_OFFSET + 0x8)
> > > > + FIELD(CXL_BI_DECODER_STATUS, COMMITTED, 0, 1)
> > > > + FIELD(CXL_BI_DECODER_STATUS, ERR_NOT_COMMITTED, 1, 1)
> > > > + FIELD(CXL_BI_DECODER_STATUS, COMMIT_TMO_SCALE, 8, 4)
> > > > + FIELD(CXL_BI_DECODER_STATUS, COMMIT_TMO_BASE, 12, 4)
> > > > +
> > > > +QEMU_BUILD_BUG_MSG((CXL_BI_DECODER_REGISTERS_OFFSET +
> > > > + CXL_BI_DECODER_REGISTERS_SIZE) >= 0x1000,
> > > > "No space for registers");
> > > >
> > > > +/* track BI explicit commit handling for route table and decoder */
> > > > +enum {
> > > > + CXL_BISTATE_RT = 0,
> > > > + CXL_BISTATE_DECODER,
> > > > + CXL_BISTATE_MAX
> > > > +};
> > > > +
> > > > +typedef struct bi_state {
> > > > + uint64_t last_commit; /* last 0->1 transition */
> > > > +} BIState;
> > > > +
> > > > typedef struct component_registers {
> > > > /*
> > > > * Main memory region to be registered with QEMU core.
> > > > @@ -259,6 +306,7 @@ typedef struct cxl_component {
> > > > };
> > > >
> > > > CDATObject cdat;
> > > > + BIState bi_state[CXL_BISTATE_MAX];
> > > > } CXLComponentState;
> > > >
> > > > void cxl_component_register_block_init(Object *obj,
> > > > @@ -266,7 +314,7 @@ void cxl_component_register_block_init(Object *obj,
> > > > const char *type);
> > > > void cxl_component_register_init_common(uint32_t *reg_state,
> > > > uint32_t *write_msk,
> > > > - enum reg_type type);
> > > > + enum reg_type type, bool bi);
> > > >
> > > > void cxl_component_create_dvsec(CXLComponentState *cxl_cstate,
> > > > enum reg_type cxl_dev_type, uint16_t length,
> > > > diff --git a/include/hw/cxl/cxl_device.h b/include/hw/cxl/cxl_device.h
> > > > index 7d9236db8c85..393f3122173b 100644
> > > > --- a/include/hw/cxl/cxl_device.h
> > > > +++ b/include/hw/cxl/cxl_device.h
> > > > @@ -770,6 +770,9 @@ struct CXLType3Dev {
> > > > CXLMemSparingReadAttrs rank_sparing_attrs;
> > > > CXLMemSparingWriteAttrs rank_sparing_wr_attrs;
> > > >
> > > > + /* BI flows */
> > > > + bool hdmdb;
> > > > +
> > > > struct dynamic_capacity {
> > > > HostMemoryBackend *host_dc;
> > > > AddressSpace host_dc_as;
> > > > diff --git a/hw/cxl/cxl-component-utils.c b/hw/cxl/cxl-component-utils.c
> > > > index 91770f103a85..a7d36e1128c2 100644
> > > > --- a/hw/cxl/cxl-component-utils.c
> > > > +++ b/hw/cxl/cxl-component-utils.c
> > > > @@ -71,10 +71,40 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
> > > > case 4:
> > > > if (cregs->special_ops && cregs->special_ops->read) {
> > > > return cregs->special_ops->read(cxl_cstate, offset, 4);
> > > > - } else {
> > > > - QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
> > > > - return cregs->cache_mem_registers[offset / 4];
> > > > }
> > > > +
> > > > + QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
> > > > +
> > > > + if (offset == A_CXL_BI_RT_STATUS ||
> > > > + offset == A_CXL_BI_DECODER_STATUS) {
> > > > + int type;
> > > > + uint64_t started;
> > > > +
> > > > + type = (offset == A_CXL_BI_RT_STATUS) ?
> > > > + CXL_BISTATE_RT : CXL_BISTATE_DECODER;
> > > > + started = cxl_cstate->bi_state[type].last_commit;
> > > > +
> > > > + if (started) {
> > > > + uint32_t *cache_mem = cregs->cache_mem_registers;
> > > > + uint32_t val = cache_mem[offset / 4];
> > > > + uint64_t now;
> > > > + int set;
> > > > +
> > > > + now = qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
> > > > + /* arbitrary 100 ms to do the commit */
> > > > + set = !!(now >= started + 100);
> > > > +
> > > > + if (offset == A_CXL_BI_RT_STATUS) {
> > > > + val = FIELD_DP32(val, CXL_BI_RT_STATUS, COMMITTED, set);
> > > > + } else {
> > > > + val = FIELD_DP32(val, CXL_BI_DECODER_STATUS, COMMITTED,
> > > > + set);
> > > > + }
> > > > + stl_le_p((uint8_t *)cache_mem + offset, val);
> > > > + }
> > > > + }
> > > > +
> > > > + return cregs->cache_mem_registers[offset / 4];
> > > > case 8:
> > > > qemu_log_mask(LOG_UNIMP,
> > > > "CXL 8 byte cache mem registers not implemented\n");
> > > > @@ -118,6 +148,47 @@ static void dumb_hdm_handler(CXLComponentState *cxl_cstate, hwaddr offset,
> > > > stl_le_p((uint8_t *)cache_mem + offset, value);
> > > > }
> > > >
> > > > +static void bi_handler(CXLComponentState *cxl_cstate, hwaddr offset,
> > > > + uint32_t value)
> > > > +{
> > > > + ComponentRegisters *cregs = &cxl_cstate->crb;
> > > > + uint32_t sts, *cache_mem = cregs->cache_mem_registers;
> > > > + bool to_commit = false;
> > > > + int type = 0; /* Unused value - work around for compiler warning */
> > > > +
> > > > + switch (offset) {
> > > > + case A_CXL_BI_RT_CTRL:
> > > > + to_commit = FIELD_EX32(value, CXL_BI_RT_CTRL, COMMIT);
> > > > + if (to_commit) {
> > > > + sts = cxl_cache_mem_read_reg(cxl_cstate,
> > > > + R_CXL_BI_RT_STATUS, 4);
> > > > + sts = FIELD_DP32(sts, CXL_BI_RT_STATUS, COMMITTED, 0);
> > > > + stl_le_p((uint8_t *)cache_mem + R_CXL_BI_RT_STATUS, sts);
> > > > + type = CXL_BISTATE_RT;
> > > > + }
> > > > + break;
> > > > + case A_CXL_BI_DECODER_CTRL:
> > > > + to_commit = FIELD_EX32(value, CXL_BI_DECODER_CTRL, COMMIT);
> > > > + if (to_commit) {
> > > > + sts = cxl_cache_mem_read_reg(cxl_cstate,
> > > > + R_CXL_BI_DECODER_STATUS, 4);
> > > > + sts = FIELD_DP32(sts, CXL_BI_DECODER_STATUS, COMMITTED, 0);
> > > > + stl_le_p((uint8_t *)cache_mem + R_CXL_BI_DECODER_STATUS, sts);
> > > > + type = CXL_BISTATE_DECODER;
> > > > + }
> > > > + break;
> > > > + default:
> > > > + break;
> > > > + }
> > > > +
> > > > + if (to_commit) {
> > > > + cxl_cstate->bi_state[type].last_commit =
> > > > + qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
> > > > + }
> > > > +
> > > > + stl_le_p((uint8_t *)cache_mem + offset, value);
> > > > +}
> > > > +
> > > > static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
> > > > unsigned size)
> > > > {
> > > > @@ -141,6 +212,9 @@ static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
> > > > if (offset >= A_CXL_HDM_DECODER_CAPABILITY &&
> > > > offset <= A_CXL_HDM_DECODER3_TARGET_LIST_HI) {
> > > > dumb_hdm_handler(cxl_cstate, offset, value);
> > > > + } else if (offset == A_CXL_BI_RT_CTRL ||
> > > > + offset == A_CXL_BI_DECODER_CTRL) {
> > > > + bi_handler(cxl_cstate, offset, value);
> > > > } else {
> > > > cregs->cache_mem_registers[offset / 4] = value;
> > > > }
> > > > @@ -230,7 +304,7 @@ static void ras_init_common(uint32_t *reg_state, uint32_t *write_msk)
> > > > }
> > > >
> > > > static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > > - enum reg_type type)
> > > > + enum reg_type type, bool bi)
> > > > {
> > > > int decoder_count = CXL_HDM_DECODER_COUNT;
> > > > int hdm_inc = R_CXL_HDM_DECODER1_BASE_LO - R_CXL_HDM_DECODER0_BASE_LO;
> > > > @@ -255,7 +329,9 @@ static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > > UIO_DECODER_COUNT, 0);
> > > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, MEMDATA_NXM_CAP, 0);
> > > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY,
> > > > - SUPPORTED_COHERENCY_MODEL, 0); /* Unknown */
> > > > + SUPPORTED_COHERENCY_MODEL,
> > > > + /* host+dev or Unknown */
> > > > + type == CXL2_TYPE3_DEVICE && bi ? 3 : 0);
> > > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_GLOBAL_CONTROL,
> > > > HDM_DECODER_ENABLE, 0);
> > > > write_msk[R_CXL_HDM_DECODER_GLOBAL_CONTROL] = 0x3;
> > > > @@ -278,9 +354,43 @@ static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > > }
> > > > }
> > > >
> > > > +static void bi_rt_init_common(uint32_t *reg_state, uint32_t *write_msk)
> > > > +{
> > > > + /* switch usp must commit the new BI-ID, timeout of 2secs */
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_CAPABILITY, EXPLICIT_COMMIT, 1);
> > > > +
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_CTRL, COMMIT, 0);
> > > > + write_msk[R_CXL_BI_RT_CTRL] = 0x1;
> > > > +
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMITTED, 0);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, ERR_NOT_COMMITTED, 0);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMIT_TMO_SCALE, 0x6);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMIT_TMO_BASE, 0x2);
> > > > +}
> > > > +
> > > > +static void bi_decoder_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > > + enum reg_type type)
> > > > +{
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CAPABILITY, HDM_D, 0);
> > > > + /* switch dsp must commit the new BI-ID, timeout of 2secs */
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CAPABILITY, EXPLICIT_COMMIT,
> > > > + (type != CXL2_ROOT_PORT && type != CXL2_TYPE3_DEVICE));
> > > > +
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, BI_FW, 0);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, BI_ENABLE, 0);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, COMMIT, 0);
> > > > + write_msk[R_CXL_BI_DECODER_CTRL] = 0x7;
> > > > +
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMITTED, 0);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, ERR_NOT_COMMITTED, 0);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMIT_TMO_SCALE, 0x6);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMIT_TMO_BASE, 0x2);
> > > > +}
> > > > +
> > > > void cxl_component_register_init_common(uint32_t *reg_state,
> > > > uint32_t *write_msk,
> > > > - enum reg_type type)
> > > > + enum reg_type type,
> > > > + bool bi)
> > > > {
> > > > int caps = 0;
> > > >
> > > > @@ -320,7 +430,7 @@ void cxl_component_register_init_common(uint32_t *reg_state,
> > > > case CXL2_LOGICAL_DEVICE:
> > > > /* + HDM */
> > > > init_cap_reg(HDM, 5, 1);
> > > > - hdm_init_common(reg_state, write_msk, type);
> > > > + hdm_init_common(reg_state, write_msk, type, bi);
> > > > /* fallthrough */
> > > > case CXL2_DOWNSTREAM_PORT:
> > > > case CXL2_DEVICE:
> > > > @@ -335,6 +445,24 @@ void cxl_component_register_init_common(uint32_t *reg_state,
> > > > abort();
> > > > }
> > > >
> > > > + /* back invalidate */
> > > > + if (bi) {
> > > > + switch (type) {
> > > > + case CXL2_UPSTREAM_PORT:
> > > > + init_cap_reg(BI_RT, 11, CXL_BI_RT_CAP_VERSION);
> > > > + bi_rt_init_common(reg_state, write_msk);
> > > > + break;
> > > > + case CXL2_ROOT_PORT:
> > > > + case CXL2_DOWNSTREAM_PORT:
> > > > + case CXL2_TYPE3_DEVICE:
> > > > + init_cap_reg(BI_DECODER, 12, CXL_BI_DECODER_CAP_VERSION);
> > > > + bi_decoder_init_common(reg_state, write_msk, type);
> > > > + break;
> > > > + default:
> > > > + break;
> > > > + }
> > > > + }
> > > > +
> > > > ARRAY_FIELD_DP32(reg_state, CXL_CAPABILITY_HEADER, ARRAY_SIZE, caps);
> > > > #undef init_cap_reg
> > > > }
> > > > diff --git a/hw/mem/cxl_type3.c b/hw/mem/cxl_type3.c
> > > > index 3c7ecd8c48bc..3f09c589ae58 100644
> > > > --- a/hw/mem/cxl_type3.c
> > > > +++ b/hw/mem/cxl_type3.c
> > > > @@ -748,6 +748,11 @@ static bool cxl_setup_memory(CXLType3Dev *ct3d, Error **errp)
> > > > return false;
> > > > }
> > > >
> > > > + if (!ct3d->flitmode && ct3d->hdmdb) {
> > > > + error_setg(errp, "hdm-db requires operating in 256b flit");
> > > > + return false;
> > > > + }
> > > > +
> > > > if (ct3d->hostvmem) {
> > > > MemoryRegion *vmr;
> > > > char *v_name;
> > > > @@ -1317,7 +1322,8 @@ static void ct3d_reset(DeviceState *dev)
> > > >
> > > > pcie_cap_fill_link_ep_usp(PCI_DEVICE(dev), ct3d->width, ct3d->speed,
> > > > ct3d->flitmode);
> > > > - cxl_component_register_init_common(reg_state, write_msk, CXL2_TYPE3_DEVICE);
> > > > + cxl_component_register_init_common(reg_state, write_msk,
> > > > + CXL2_TYPE3_DEVICE, ct3d->hdmdb);
> > > > cxl_device_register_init_t3(ct3d, CXL_T3_MSIX_MBOX);
> > > >
> > > > /*
> > > > @@ -1356,6 +1362,7 @@ static const Property ct3_props[] = {
> > > > DEFINE_PROP_PCIE_LINK_WIDTH("x-width", CXLType3Dev,
> > > > width, PCIE_LINK_WIDTH_16),
> > > > DEFINE_PROP_BOOL("x-256b-flit", CXLType3Dev, flitmode, false),
> > > > + DEFINE_PROP_BOOL("hdm-db", CXLType3Dev, hdmdb, false),
> > > > };
> > > >
> > > > static uint64_t get_lsa_size(CXLType3Dev *ct3d)
> > > > diff --git a/hw/pci-bridge/cxl_downstream.c b/hw/pci-bridge/cxl_downstream.c
> > > > index 64086d8ec2f2..320818a8f1ce 100644
> > > > --- a/hw/pci-bridge/cxl_downstream.c
> > > > +++ b/hw/pci-bridge/cxl_downstream.c
> > > > @@ -39,7 +39,7 @@ static void latch_registers(CXLDownstreamPort *dsp)
> > > > uint32_t *write_msk = dsp->cxl_cstate.crb.cache_mem_regs_write_mask;
> > > >
> > > > cxl_component_register_init_common(reg_state, write_msk,
> > > > - CXL2_DOWNSTREAM_PORT);
> > > > + CXL2_DOWNSTREAM_PORT, true);
> > > > }
> > > >
> > > > /* TODO: Look at sharing this code across all CXL port types */
> > > > diff --git a/hw/pci-bridge/cxl_root_port.c b/hw/pci-bridge/cxl_root_port.c
> > > > index 5641048084a4..e2093ac39ee6 100644
> > > > --- a/hw/pci-bridge/cxl_root_port.c
> > > > +++ b/hw/pci-bridge/cxl_root_port.c
> > > > @@ -101,7 +101,8 @@ static void latch_registers(CXLRootPort *crp)
> > > > uint32_t *reg_state = crp->cxl_cstate.crb.cache_mem_registers;
> > > > uint32_t *write_msk = crp->cxl_cstate.crb.cache_mem_regs_write_mask;
> > > >
> > > > - cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT);
> > > > + cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT,
> > > > + true);
> > > > }
> > > >
> > > > static void build_dvsecs(PCIDevice *d, CXLComponentState *cxl)
> > > > diff --git a/hw/pci-bridge/cxl_upstream.c b/hw/pci-bridge/cxl_upstream.c
> > > > index c352d11dc7b7..fb8d19539c9f 100644
> > > > --- a/hw/pci-bridge/cxl_upstream.c
> > > > +++ b/hw/pci-bridge/cxl_upstream.c
> > > > @@ -90,7 +90,7 @@ static void latch_registers(CXLUpstreamPort *usp)
> > > > uint32_t *write_msk = usp->cxl_cstate.crb.cache_mem_regs_write_mask;
> > > >
> > > > cxl_component_register_init_common(reg_state, write_msk,
> > > > - CXL2_UPSTREAM_PORT);
> > > > + CXL2_UPSTREAM_PORT, usp->flitmode);
> > > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, TARGET_COUNT, 8);
> > > > }
> > > >
> > > > diff --git a/hw/pci-bridge/pci_expander_bridge.c b/hw/pci-bridge/pci_expander_bridge.c
> > > > index b6e2eb796951..11623a5666f6 100644
> > > > --- a/hw/pci-bridge/pci_expander_bridge.c
> > > > +++ b/hw/pci-bridge/pci_expander_bridge.c
> > > > @@ -300,7 +300,7 @@ static void pxb_cxl_dev_reset(DeviceState *dev)
> > > > uint32_t *write_msk = cxl_cstate->crb.cache_mem_regs_write_mask;
> > > > int dsp_count = 0;
> > > >
> > > > - cxl_component_register_init_common(reg_state, write_msk, CXL2_RC);
> > > > + cxl_component_register_init_common(reg_state, write_msk, CXL2_RC, false);
> > > > /*
> > > > * The CXL specification allows for host bridges with no HDM decoders
> > > > * if they only have a single root port.
> > > > --
> > > > 2.51.0
> >
> >
^ permalink raw reply [flat|nested] 14+ messages in thread
* [PATCH qemu v6 7/7] hw/cxl: Remove register special_ops->read()
2026-02-04 12:12 [PATCH qemu v6 0/7] hw/cxl: Support Back-Invalidate (+ PCIe Flit mode) Jonathan Cameron
` (5 preceding siblings ...)
2026-02-04 12:12 ` [PATCH qemu v6 6/7] hw/cxl: Support type3 HDM-DB Jonathan Cameron
@ 2026-02-04 12:12 ` Jonathan Cameron
6 siblings, 0 replies; 14+ messages in thread
From: Jonathan Cameron @ 2026-02-04 12:12 UTC (permalink / raw)
To: Michael Tsirkin, qemu-devel, Davidlohr Bueso
Cc: linuxarm, linux-cxl, Ravi Shankar, Marcel Apfelbaum,
Markus Armbruster, Michael Roth
From: Davidlohr Bueso <dave@stgolabs.net>
... this is unused, unlike its write counterpart.
Suggested-by: Jonathan.Cameron@huawei.com
Tested-by: Dongjoo Seo <dongjoo.seo1@samsung.com>
Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
hw/cxl/cxl-component-utils.c | 4 ----
1 file changed, 4 deletions(-)
diff --git a/hw/cxl/cxl-component-utils.c b/hw/cxl/cxl-component-utils.c
index a7d36e1128c2..a3077184e230 100644
--- a/hw/cxl/cxl-component-utils.c
+++ b/hw/cxl/cxl-component-utils.c
@@ -69,10 +69,6 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
switch (size) {
case 4:
- if (cregs->special_ops && cregs->special_ops->read) {
- return cregs->special_ops->read(cxl_cstate, offset, 4);
- }
-
QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
if (offset == A_CXL_BI_RT_STATUS ||
--
2.51.0
^ permalink raw reply related [flat|nested] 14+ messages in thread