diff options
| author | Michael S. Tsirkin <mst@redhat.com> | 2014-09-11 18:45:33 +0200 |
|---|---|---|
| committer | Michael S. Tsirkin <mst@redhat.com> | 2014-09-18 21:51:24 +0300 |
| commit | e43c0b2ea5574efb0bedebf6a7d05916eefeba52 (patch) | |
| tree | 9118e75f9f8fb9635eb96bb04bd2316dc314587b | |
| parent | 9e8e8c48653471fa5fed447e388fdef57d4f6998 (diff) | |
virtio-pci: enable bus master for old guests
commit cc943c36faa192cd4b32af8fe5edb31894017d35
pci: Use bus master address space for delivering MSI/MSI-X messages
breaks virtio-net for rhel6.[56] x86 guests because they don't
enable bus mastering for virtio PCI devices. For the same reason,
rhel6.[56] ppc64 guests cannot boot on a virtio-blk disk anymore.
Old guests forgot to enable bus mastering, enable it automatically on
DRIVER (guests use some devices before DRIVER_OK).
Reported-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Reviewed-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Tested-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
| -rw-r--r-- | hw/virtio/virtio-pci.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c index ddb5da181c..a827cd41bf 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. */ |