[Qemu-devel] [PATCH v2] vfio/pci: fix out-of-sync BAR information on reset

[Ido Yariv <ido@wizery.com>]

When a PCI device is reset, pci_do_device_reset resets all BAR addresses
in the relevant PCIDevice's config buffer.

The VFIO configuration space stays untouched, so the guest OS may choose
to skip restoring the BAR addresses as they would seem intact. The PCI
device may be left non-operational.
One example of such a scenario is when the guest exits S3.

Fix this by resetting the BAR addresses in the VFIO configuration space
as well.

Signed-off-by: Ido Yariv <ido@wizery.com>
---
 hw/vfio/pci.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index 65d30fd..b399742 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -1922,11 +1922,23 @@ static void vfio_pci_pre_reset(VFIOPCIDevice *vdev)
 static void vfio_pci_post_reset(VFIOPCIDevice *vdev)
 {
     Error *err = NULL;
+    int nr;
 
     vfio_intx_enable(vdev, &err);
     if (err) {
         error_reportf_err(err, ERR_PREFIX, vdev->vbasedev.name);
     }
+
+    for (nr = 0; nr < PCI_NUM_REGIONS - 1; ++nr) {
+        off_t addr = vdev->config_offset + PCI_BASE_ADDRESS_0 + (4 * nr);
+        uint32_t val = 0;
+        uint32_t len = sizeof(val);
+
+        if (pwrite(vdev->vbasedev.fd, &val, len, addr) != len) {
+            error_report("%s(%s) reset bar %d failed: %m", __func__,
+                         vdev->vbasedev.name, nr);
+        }
+    }
 }
 
 static bool vfio_pci_host_match(PCIHostDeviceAddress *addr, const char *name)
-- 
2.7.4