[PATCH v4 5/5] vpci: add SR-IOV support for DomUs

[Mykyta Poturai <Mykyta_Poturai@xxxxxxxx>]

From: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>

Emulate guest BAR register values based on PF BAR values for VFs.
This allows creating a guest view of the normal BAR registers and emulates
the size and properties as it is done during PCI device enumeration by
the guest.

Expose VID/DID and class/revision to the guest.

Note, that VFs ROM BAR is read-only and is all zeros, but VF may provide
access to the PFs ROM via emulation and is not implemented.

Note this only removes one of the gaps on the way to vPCI DomU support;
VFs are not usable in DomUs until the rest of it is upstream. The DomU
testing behind this patch used out-of-tree vPCI DomU patches.

Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
Signed-off-by: Mykyta Poturai <mykyta_poturai@xxxxxxxx>
---
v3->v4:
* emulate VID/DID again
* add a note to commit message

v2->v3:
* don't emulate VID/DID registers
* replace ifdef with IS_ENABLED

v1->v2:
* remove VF register handlers covered by init_header
* set guest addr unconditionally
---
 xen/drivers/vpci/sriov.c | 65 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 63 insertions(+), 2 deletions(-)

diff --git a/xen/drivers/vpci/sriov.c b/xen/drivers/vpci/sriov.c
index 4e09bdfbfd..024a099822 100644
--- a/xen/drivers/vpci/sriov.c
+++ b/xen/drivers/vpci/sriov.c
@@ -79,19 +79,80 @@ int vpci_vf_init_header(struct pci_dev *vf_pdev)
     const struct pci_dev *pf_pdev;
     int rc = 0;
     uint16_t ctrl;
+    unsigned int sriov_pos;
 
     ASSERT(rw_is_write_locked(&vf_pdev->domain->pci_lock));
     ASSERT(vf_pdev->info.is_virtfn);
 
     pf_pdev = vf_pdev->pf_pdev;
     ASSERT(pf_pdev);
+    sriov_pos = pf_pdev->vpci->sriov->pos;
 
     rc = vf_init_bars(vf_pdev);
     if ( rc )
         return rc;
 
-    ctrl = pci_conf_read16(pf_pdev->sbdf,
-                           pf_pdev->vpci->sriov->pos + PCI_SRIOV_CTRL);
+    ctrl = pci_conf_read16(pf_pdev->sbdf, sriov_pos + PCI_SRIOV_CTRL);
+
+    if ( IS_ENABLED(CONFIG_HAS_VPCI_GUEST_SUPPORT) &&
+         pf_pdev->domain != vf_pdev->domain )
+    {
+        struct vpci_bar *bars = vf_pdev->vpci->header.bars;
+        /*
+         * A VF's Vendor and Device ID registers read as 0xffff. The guest has
+         * no PF to synthesise them from, so take the vendor from the PF and
+         * the device from its SR-IOV capability.
+         */
+        uint16_t vid = pci_conf_read16(pf_pdev->sbdf, PCI_VENDOR_ID);
+        uint16_t did = pci_conf_read16(pf_pdev->sbdf,
+                                       sriov_pos + PCI_SRIOV_VF_DID);
+
+        rc = vpci_add_register(vf_pdev->vpci, vpci_read_val, NULL,
+                               PCI_VENDOR_ID, 2, (void *)(uintptr_t)vid);
+        if ( rc )
+            return rc;
+
+        rc = vpci_add_register(vf_pdev->vpci, vpci_read_val, NULL,
+                               PCI_DEVICE_ID, 2, (void *)(uintptr_t)did);
+        if ( rc )
+            return rc;
+
+        /* Hardcode multi-function device bit to 0 */
+        rc = vpci_add_register(vf_pdev->vpci, vpci_read_val, NULL,
+                               PCI_HEADER_TYPE, 1,
+                               (void *)PCI_HEADER_TYPE_NORMAL);
+        if ( rc )
+            return rc;
+
+        rc = vpci_add_register(vf_pdev->vpci, vpci_hw_read32, NULL,
+                               PCI_CLASS_REVISION, 4, NULL);
+        if ( rc )
+            return rc;
+
+        for ( unsigned int i = 0; i < PCI_SRIOV_NUM_BARS; i++ )
+        {
+            switch ( pf_pdev->vpci->sriov->vf_bars[i].type )
+            {
+            case VPCI_BAR_MEM32:
+            case VPCI_BAR_MEM64_LO:
+            case VPCI_BAR_MEM64_HI:
+                rc = vpci_add_register(vf_pdev->vpci, vpci_guest_mem_bar_read,
+                                       vpci_guest_mem_bar_write,
+                                       PCI_BASE_ADDRESS_0 + i * 4, 4, 
&bars[i]);
+                if ( rc )
+                    return rc;
+                break;
+
+            default:
+                rc = vpci_add_register(vf_pdev->vpci, vpci_read_val, NULL,
+                                       PCI_BASE_ADDRESS_0 + i * 4, 4,
+                                       (void *)0);
+                if ( rc )
+                    return rc;
+                break;
+            }
+        }
+    }
 
     if ( (pf_pdev->domain == vf_pdev->domain) && (ctrl & PCI_SRIOV_CTRL_MSE) )
     {
-- 
2.55.0