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virtio-pci: fix bus master work around on load

PATCH In review Michael S. Tsirkin 2 participants 2 messages Mar 19, 2011 – Mar 21, 2011

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Michael S. Tsirkin

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PATCH 1/1 virtio-pci: fix bus master work around on load

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 <[email protected]>
Cc Alexander Graf <[email protected]>
---
 hw/virtio-pci.c |   13 ++++++-------
 hw/virtio.h     |    1 +
 2 files changed, 7 insertions(+), 7 deletions(-)
hw/virtio-pci.c +6 -7
index 3911b09..d40ac23 100644
@@ -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);
Signature · 1 line
1.7.3.2.91.g446ac
#1 lore raw
Quoted 7 lines · 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.

Quoted 7 lines

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 <[email protected]>
Cc Alexander Graf <[email protected]>

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

Alex