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-rw-r--r--hw/virtio/virtio-pci.c10
1 files changed, 10 insertions, 0 deletions
diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index ddb5da1..a827cd4 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -314,6 +314,16 @@ static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val)
msix_unuse_all_vectors(&proxy->pci_dev);
}
+ /* Linux before 2.6.34 drives the device without enabling
+ the PCI device bus master bit. Enable it automatically
+ for the guest. This is a PCI spec violation but so is
+ initiating DMA with bus master bit clear. */
+ if (val == (VIRTIO_CONFIG_S_ACKNOWLEDGE | VIRTIO_CONFIG_S_DRIVER)) {
+ pci_default_write_config(&proxy->pci_dev, PCI_COMMAND,
+ proxy->pci_dev.config[PCI_COMMAND] |
+ PCI_COMMAND_MASTER, 1);
+ }
+
/* Linux before 2.6.34 sets the device as OK without enabling
the PCI device bus master bit. In this case we need to disable
some safety checks. */