[RFC PATCH v4 06/38] NTB: epf: Add mwN_offset support and config region versioning

Koichiro Den
2026-01-18T13:55:07Z

Introduce new mwN_offset configfs attributes to specify memory window
offsets. This enables mapping multiple windows into a single BAR at
arbitrary offsets, improving layout flexibility.

Extend the control register region and add a 32-bit config version
field. Reuse the unused NTB_EPF_TOPOLOGY offset (0x0C) for a version
field. The endpoint function driver writes 1 (NTB_EPF_CTRL_VERSION_V1),
and ntb_hw_epf reads it at probe time and refuses to bind to unknown
versions.

Compatibility matrix:

| EP v1 | EP legacy
----------+-------+----------
RC v1 | v1 | legacy
RC legacy | ? (*) | legacy

(*) An unpatched (legacy) RC may misinterpret the paired EP's intention
and program MW layout incorrectly when offsets are used.

Signed-off-by: Koichiro Den <den@valinux.co.jp>
---
drivers/ntb/hw/epf/ntb_hw_epf.c | 60 +++++++-
drivers/pci/endpoint/functions/pci-epf-vntb.c | 136 ++++++++++++++++--
2 files changed, 176 insertions(+), 20 deletions(-)

diff --git a/drivers/ntb/hw/epf/ntb_hw_epf.c b/drivers/ntb/hw/epf/ntb_hw_epf.c
index 9935da48a52e..4b3fa996219a 100644
--- a/drivers/ntb/hw/epf/ntb_hw_epf.c
+++ b/drivers/ntb/hw/epf/ntb_hw_epf.c
@@ -30,18 +30,27 @@
#define NTB_EPF_LINK_STATUS 0x0A
#define LINK_STATUS_UP BIT(0)

-#define NTB_EPF_TOPOLOGY 0x0C
+/*
+ * Legacy unused NTB_EPF_TOPOLOGY (0x0c) is repurposed as a control version
+ * field
+ */
+#define NTB_EPF_CTRL_VERSION 0x0C
#define NTB_EPF_LOWER_ADDR 0x10
#define NTB_EPF_UPPER_ADDR 0x14
#define NTB_EPF_LOWER_SIZE 0x18
#define NTB_EPF_UPPER_SIZE 0x1C
#define NTB_EPF_MW_COUNT 0x20
-#define NTB_EPF_MW1_OFFSET 0x24
+#define NTB_EPF_MW1_OFFSET 0x24 /* used by legacy (version=0) only */
#define NTB_EPF_SPAD_OFFSET 0x28
#define NTB_EPF_SPAD_COUNT 0x2C
#define NTB_EPF_DB_ENTRY_SIZE 0x30
#define NTB_EPF_DB_DATA(n) (0x34 + (n) * 4)
#define NTB_EPF_DB_OFFSET(n) (0xB4 + (n) * 4)
+#define NTB_EPF_MW_OFFSET(n) (0x134 + (n) * 4)
+#define NTB_EPF_MW_SIZE(n) (0x144 + (n) * 4)
+
+#define NTB_EPF_CTRL_VERSION_LEGACY 0
+#define NTB_EPF_CTRL_VERSION_V1 1

#define NTB_EPF_MIN_DB_COUNT 3
#define NTB_EPF_MAX_DB_COUNT 31
@@ -451,11 +460,22 @@ static int ntb_epf_peer_mw_get_addr(struct ntb_dev *ntb, int idx,
phys_addr_t *base, resource_size_t *size)
{
struct ntb_epf_dev *ndev = ntb_ndev(ntb);
- u32 offset = 0;
+ resource_size_t bar_sz;
+ u32 offset, sz, ver;
int bar;

- if (idx == 0)
- offset = readl(ndev->ctrl_reg + NTB_EPF_MW1_OFFSET);
+ ver = readl(ndev->ctrl_reg + NTB_EPF_CTRL_VERSION);
+ if (ver == NTB_EPF_CTRL_VERSION_LEGACY) {
+ /* Legacy layout: only MW1 offset exists, and there is no MW_SIZE[] */
+ if (idx == 0)
+ offset = readl(ndev->ctrl_reg + NTB_EPF_MW1_OFFSET);
+ else
+ offset = 0;
+ sz = 0;
+ } else {
+ offset = readl(ndev->ctrl_reg + NTB_EPF_MW_OFFSET(idx));
+ sz = readl(ndev->ctrl_reg + NTB_EPF_MW_SIZE(idx));
+ }

bar = ntb_epf_mw_to_bar(ndev, idx);
if (bar < 0)
@@ -464,8 +484,11 @@ static int ntb_epf_peer_mw_get_addr(struct ntb_dev *ntb, int idx,
if (base)
*base = pci_resource_start(ndev->ntb.pdev, bar) + offset;

- if (size)
- *size = pci_resource_len(ndev->ntb.pdev, bar) - offset;
+ if (size) {
+ bar_sz = pci_resource_len(ndev->ntb.pdev, bar);
+ *size = sz ? min_t(resource_size_t, sz, bar_sz - offset)
+ : (bar_sz > offset ? bar_sz - offset : 0);
+ }

return 0;
}
@@ -547,6 +570,25 @@ static inline void ntb_epf_init_struct(struct ntb_epf_dev *ndev,
ndev->ntb.ops = &ntb_epf_ops;
}

+static int ntb_epf_check_version(struct ntb_epf_dev *ndev)
+{
+ struct device *dev = ndev->dev;
+ u32 ver;
+
+ ver = readl(ndev->ctrl_reg + NTB_EPF_CTRL_VERSION);
+
+ switch (ver) {
+ case NTB_EPF_CTRL_VERSION_LEGACY:
+ case NTB_EPF_CTRL_VERSION_V1:
+ break;
+ default:
+ dev_err(dev, "Unsupported NTB EPF version %u\n", ver);
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
static int ntb_epf_init_dev(struct ntb_epf_dev *ndev)
{
struct device *dev = ndev->dev;
@@ -696,6 +738,10 @@ static int ntb_epf_pci_probe(struct pci_dev *pdev,
return ret;
}

+ ret = ntb_epf_check_version(ndev);
+ if (ret)
+ return ret;
+
ret = ntb_epf_init_dev(ndev);
if (ret) {
dev_err(dev, "Failed to init device\n");
diff --git a/drivers/pci/endpoint/functions/pci-epf-vntb.c b/drivers/pci/endpoint/functions/pci-epf-vntb.c
index c08d349db350..4927faa28255 100644
--- a/drivers/pci/endpoint/functions/pci-epf-vntb.c
+++ b/drivers/pci/endpoint/functions/pci-epf-vntb.c
@@ -39,6 +39,7 @@
#include <linux/atomic.h>
#include <linux/delay.h>
#include <linux/io.h>
+#include <linux/log2.h>
#include <linux/module.h>
#include <linux/slab.h>

@@ -61,6 +62,7 @@ static struct workqueue_struct *kpcintb_workqueue;

#define LINK_STATUS_UP BIT(0)

+#define CTRL_VERSION 1
#define SPAD_COUNT 64
#define DB_COUNT 4
#define NTB_MW_OFFSET 2
@@ -107,7 +109,7 @@ struct epf_ntb_ctrl {
u32 argument;
u16 command_status;
u16 link_status;
- u32 topology;
+ u32 version;
u64 addr;
u64 size;
u32 num_mws;
@@ -117,6 +119,8 @@ struct epf_ntb_ctrl {
u32 db_entry_size;
u32 db_data[MAX_DB_COUNT];
u32 db_offset[MAX_DB_COUNT];
+ u32 mw_offset[MAX_MW];
+ u32 mw_size[MAX_MW];
} __packed;

struct epf_ntb {
@@ -128,6 +132,7 @@ struct epf_ntb {
u32 db_count;
u32 spad_count;
u64 mws_size[MAX_MW];
+ u64 mws_offset[MAX_MW];
atomic64_t db;
u32 vbus_number;
u16 vntb_pid;
@@ -460,10 +465,13 @@ static int epf_ntb_config_spad_bar_alloc(struct epf_ntb *ntb)
ntb->reg = base;

ctrl = ntb->reg;
+ ctrl->version = CTRL_VERSION;
ctrl->spad_offset = ctrl_size;

ctrl->spad_count = spad_count;
ctrl->num_mws = ntb->num_mws;
+ memset(ctrl->mw_offset, 0, sizeof(ctrl->mw_offset));
+ memset(ctrl->mw_size, 0, sizeof(ctrl->mw_size));
ntb->spad_size = spad_size;

ctrl->db_entry_size = sizeof(u32);
@@ -695,15 +703,31 @@ static void epf_ntb_db_bar_clear(struct epf_ntb *ntb)
*/
static int epf_ntb_mw_bar_init(struct epf_ntb *ntb)
{
+ struct device *dev = &ntb->epf->dev;
+ u64 bar_ends[BAR_5 + 1] = { 0 };
+ unsigned long bars_used = 0;
+ enum pci_barno barno;
+ u64 off, size, end;
int ret = 0;
int i;
- u64 size;
- enum pci_barno barno;
- struct device *dev = &ntb->epf->dev;

for (i = 0; i < ntb->num_mws; i++) {
- size = ntb->mws_size[i];
barno = ntb->epf_ntb_bar[BAR_MW1 + i];
+ off = ntb->mws_offset[i];
+ size = ntb->mws_size[i];
+ end = off + size;
+ if (end > bar_ends[barno])
+ bar_ends[barno] = end;
+ bars_used |= BIT(barno);
+ }
+
+ for (barno = BAR_0; barno <= BAR_5; barno++) {
+ if (!(bars_used & BIT(barno)))
+ continue;
+ if (bar_ends[barno] < SZ_4K)
+ size = SZ_4K;
+ else
+ size = roundup_pow_of_two(bar_ends[barno]);

ntb->epf->bar[barno].barno = barno;
ntb->epf->bar[barno].size = size;
@@ -719,8 +743,12 @@ static int epf_ntb_mw_bar_init(struct epf_ntb *ntb)
&ntb->epf->bar[barno]);
if (ret) {
dev_err(dev, "MW set failed\n");
- goto err_alloc_mem;
+ goto err_set_bar;
}
+ }
+
+ for (i = 0; i < ntb->num_mws; i++) {
+ size = ntb->mws_size[i];

/* Allocate EPC outbound memory windows to vpci vntb device */
ntb->vpci_mw_addr[i] = pci_epc_mem_alloc_addr(ntb->epf->epc,
@@ -729,19 +757,31 @@ static int epf_ntb_mw_bar_init(struct epf_ntb *ntb)
if (!ntb->vpci_mw_addr[i]) {
ret = -ENOMEM;
dev_err(dev, "Failed to allocate source address\n");
- goto err_set_bar;
+ goto err_alloc_mem;
}
}

+ for (i = 0; i < ntb->num_mws; i++) {
+ ntb->reg->mw_offset[i] = (u32)ntb->mws_offset[i];
+ ntb->reg->mw_size[i] = (u32)ntb->mws_size[i];
+ }
+
return ret;

-err_set_bar:
- pci_epc_clear_bar(ntb->epf->epc,
- ntb->epf->func_no,
- ntb->epf->vfunc_no,
- &ntb->epf->bar[barno]);
err_alloc_mem:
- epf_ntb_mw_bar_clear(ntb, i);
+ while (--i >= 0)
+ pci_epc_mem_free_addr(ntb->epf->epc,
+ ntb->vpci_mw_phy[i],
+ ntb->vpci_mw_addr[i],
+ ntb->mws_size[i]);
+err_set_bar:
+ while (--barno >= BAR_0)
+ if (bars_used & BIT(barno))
+ pci_epc_clear_bar(ntb->epf->epc,
+ ntb->epf->func_no,
+ ntb->epf->vfunc_no,
+ &ntb->epf->bar[barno]);
+
return ret;
}

@@ -1034,6 +1074,60 @@ static ssize_t epf_ntb_##_name##_store(struct config_item *item, \
return len; \
}

+#define EPF_NTB_MW_OFF_R(_name) \
+static ssize_t epf_ntb_##_name##_show(struct config_item *item, \
+ char *page) \
+{ \
+ struct config_group *group = to_config_group(item); \
+ struct epf_ntb *ntb = to_epf_ntb(group); \
+ struct device *dev = &ntb->epf->dev; \
+ int win_no, idx; \
+ \
+ if (sscanf(#_name, "mw%d_offset", &win_no) != 1) \
+ return -EINVAL; \
+ \
+ idx = win_no - 1; \
+ if (idx < 0 || idx >= ntb->num_mws) { \
+ dev_err(dev, "MW%d out of range (num_mws=%d)\n", \
+ win_no, ntb->num_mws); \
+ return -EINVAL; \
+ } \
+ \
+ idx = array_index_nospec(idx, ntb->num_mws); \
+ return sprintf(page, "%llu\n", ntb->mws_offset[idx]); \
+}
+
+#define EPF_NTB_MW_OFF_W(_name) \
+static ssize_t epf_ntb_##_name##_store(struct config_item *item, \
+ const char *page, size_t len) \
+{ \
+ struct config_group *group = to_config_group(item); \
+ struct epf_ntb *ntb = to_epf_ntb(group); \
+ struct device *dev = &ntb->epf->dev; \
+ int win_no, idx; \
+ u64 val; \
+ int ret; \
+ \
+ ret = kstrtou64(page, 0, &val); \
+ if (ret) \
+ return ret; \
+ \
+ if (sscanf(#_name, "mw%d_offset", &win_no) != 1) \
+ return -EINVAL; \
+ \
+ idx = win_no - 1; \
+ if (idx < 0 || idx >= ntb->num_mws) { \
+ dev_err(dev, "MW%d out of range (num_mws=%d)\n", \
+ win_no, ntb->num_mws); \
+ return -EINVAL; \
+ } \
+ \
+ idx = array_index_nospec(idx, ntb->num_mws); \
+ ntb->mws_offset[idx] = val; \
+ \
+ return len; \
+}
+
#define EPF_NTB_BAR_R(_name, _id) \
static ssize_t epf_ntb_##_name##_show(struct config_item *item, \
char *page) \
@@ -1104,6 +1198,14 @@ EPF_NTB_MW_R(mw3)
EPF_NTB_MW_W(mw3)
EPF_NTB_MW_R(mw4)
EPF_NTB_MW_W(mw4)
+EPF_NTB_MW_OFF_R(mw1_offset)
+EPF_NTB_MW_OFF_W(mw1_offset)
+EPF_NTB_MW_OFF_R(mw2_offset)
+EPF_NTB_MW_OFF_W(mw2_offset)
+EPF_NTB_MW_OFF_R(mw3_offset)
+EPF_NTB_MW_OFF_W(mw3_offset)
+EPF_NTB_MW_OFF_R(mw4_offset)
+EPF_NTB_MW_OFF_W(mw4_offset)
EPF_NTB_BAR_R(ctrl_bar, BAR_CONFIG)
EPF_NTB_BAR_W(ctrl_bar, BAR_CONFIG)
EPF_NTB_BAR_R(db_bar, BAR_DB)
@@ -1124,6 +1226,10 @@ CONFIGFS_ATTR(epf_ntb_, mw1);
CONFIGFS_ATTR(epf_ntb_, mw2);
CONFIGFS_ATTR(epf_ntb_, mw3);
CONFIGFS_ATTR(epf_ntb_, mw4);
+CONFIGFS_ATTR(epf_ntb_, mw1_offset);
+CONFIGFS_ATTR(epf_ntb_, mw2_offset);
+CONFIGFS_ATTR(epf_ntb_, mw3_offset);
+CONFIGFS_ATTR(epf_ntb_, mw4_offset);
CONFIGFS_ATTR(epf_ntb_, vbus_number);
CONFIGFS_ATTR(epf_ntb_, vntb_pid);
CONFIGFS_ATTR(epf_ntb_, vntb_vid);
@@ -1142,6 +1248,10 @@ static struct configfs_attribute *epf_ntb_attrs[] = {
&epf_ntb_attr_mw2,
&epf_ntb_attr_mw3,
&epf_ntb_attr_mw4,
+ &epf_ntb_attr_mw1_offset,
+ &epf_ntb_attr_mw2_offset,
+ &epf_ntb_attr_mw3_offset,
+ &epf_ntb_attr_mw4_offset,
&epf_ntb_attr_vbus_number,
&epf_ntb_attr_vntb_pid,
&epf_ntb_attr_vntb_vid,
--
2.51.0