[Qemu-devel] [PATCH master, stable] virtio-pci: fix bus master work around on load

[Qemu-devel] [PATCH master, stable] virtio-pci: fix bus master work around on load

[Michael S. Tsirkin]

Commit c81131db15dd1844d0db1d51f3cd7a105cfd2cf3
detects old guests by comparing virtio and
PCI status. It attempts to do this on load,
as well, but load_config callback in a binding
is invoked too early and so the virtio status
isn't set yet.

We could add yet another callback to the
binding, to invoke after load, but it
seems easier to reuse the existing vmstate
callback.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Cc: Alexander Graf <agraf@suse.de>
---
 hw/virtio-pci.c |   13 ++++++-------
 hw/virtio.h     |    1 +
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
index 3911b09..d40ac23 100644
--- a/hw/virtio-pci.c
+++ b/hw/virtio-pci.c
@@ -160,13 +160,6 @@ static int virtio_pci_load_config(void * opaque, QEMUFile *f)
     if (proxy->vdev->config_vector != VIRTIO_NO_VECTOR) {
         return msix_vector_use(&proxy->pci_dev, proxy->vdev->config_vector);
     }
-
-    /* Try to find out if the guest has bus master disabled, but is
-       in ready state. Then we have a buggy guest OS. */
-    if ((proxy->vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) &&
-        !(proxy->pci_dev.config[PCI_COMMAND] & PCI_COMMAND_MASTER)) {
-        proxy->flags |= VIRTIO_PCI_FLAG_BUS_MASTER_BUG;
-    }
     return 0;
 }
 
@@ -651,6 +644,12 @@ static void virtio_pci_vmstate_change(void *opaque, bool running)
     VirtIOPCIProxy *proxy = opaque;
 
     if (running) {
+        /* Try to find out if the guest has bus master disabled, but is
+           in ready state. Then we have a buggy guest OS. */
+        if ((proxy->vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) &&
+            !(proxy->pci_dev.config[PCI_COMMAND] & PCI_COMMAND_MASTER)) {
+            proxy->flags |= VIRTIO_PCI_FLAG_BUS_MASTER_BUG;
+        }
         virtio_pci_start_ioeventfd(proxy);
     } else {
         virtio_pci_stop_ioeventfd(proxy);
-- 
1.7.3.2.91.g446ac

[Qemu-devel] Re: [PATCH master, stable] virtio-pci: fix bus master work around on load

[Alexander Graf]

On 19.03.2011, at 23:30, Michael S. Tsirkin wrote:

> Commit c81131db15dd1844d0db1d51f3cd7a105cfd2cf3
> detects old guests by comparing virtio and
> PCI status. It attempts to do this on load,
> as well, but load_config callback in a binding
> is invoked too early and so the virtio status
> isn't set yet.
> 
> We could add yet another callback to the
> binding, to invoke after load, but it
> seems easier to reuse the existing vmstate
> callback.
> 
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> Cc: Alexander Graf <agraf@suse.de>

Looks good to me. I assume you have tested the code by running an old guest?


Alex