[PATCH] xio3130_downstream: Add ACS (Access Control Services) capability

[wlfightup <wlfightup@gmail.com>]

When vfio-pci devices are attached to the downstream, pcie acs
capability may be needed, Consistent with physical machine.

It has been tested in our environment, and pcie acs capability
is required in some scenarios.

Claim ACS support in the downstream port to allow
passthrough of individual functions of a device to different
guests (in a nested virt.setting) with VFIO.
Without this patch, all functions of a device, such as all VFs of
an SR/IOV device, will end up in the same IOMMU group.
A similar situation occurs on Windows with Hyper-V.

Signed-off-by: wlfightup <wlfightup@gmail.com>
---
 hw/pci-bridge/xio3130_downstream.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/hw/pci-bridge/xio3130_downstream.c b/hw/pci-bridge/xio3130_downstream.c
index 38a2361fa2..2017cf42a3 100644
--- a/hw/pci-bridge/xio3130_downstream.c
+++ b/hw/pci-bridge/xio3130_downstream.c
@@ -40,6 +40,8 @@
 #define XIO3130_SSVID_SSID              0
 #define XIO3130_EXP_OFFSET              0x90
 #define XIO3130_AER_OFFSET              0x100
+#define XIO3130_ACS_OFFSET \
+        (XIO3130_AER_OFFSET + PCI_ERR_SIZEOF)
 
 static void xio3130_downstream_write_config(PCIDevice *d, uint32_t address,
                                          uint32_t val, int len)
@@ -111,6 +113,10 @@ static void xio3130_downstream_realize(PCIDevice *d, Error **errp)
         goto err;
     }
 
+    if (!s->disable_acs) {
+        pcie_acs_init(d, XIO3130_ACS_OFFSET);
+    }
+
     return;
 
 err:
@@ -137,6 +143,7 @@ static void xio3130_downstream_exitfn(PCIDevice *d)
 static Property xio3130_downstream_props[] = {
     DEFINE_PROP_BIT(COMPAT_PROP_PCP, PCIDevice, cap_present,
                     QEMU_PCIE_SLTCAP_PCP_BITNR, true),
+    DEFINE_PROP_BOOL("x-disable-acs", PCIESlot, disable_acs, true),
     DEFINE_PROP_END_OF_LIST()
 };
 
-- 
2.24.3 (Apple Git-128)