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Subject[001/205] virtio-pci: disable msi at startup
2.6.34-stable review patch.  If anyone has any objections, please let us know.


From: Michael S. Tsirkin <>

commit b03214d559471359e2a85ae256686381d0672f29 upstream.

virtio-pci resets the device at startup by writing to the status
register, but this does not clear the pci config space,
specifically msi enable status which affects register

This breaks things like kdump when they try to use e.g. virtio-blk.

Fix by forcing msi off at startup. Since pci.c already has
a routine to do this, we export and use it instead of duplicating code.

Signed-off-by: Michael S. Tsirkin <>
Tested-by: Vivek Goyal <>
Acked-by: Jesse Barnes <>
Signed-off-by: Rusty Russell <>
Signed-off-by: Greg Kroah-Hartman <>

drivers/pci/pci.c | 1 +
drivers/virtio/virtio_pci.c | 3 +++
2 files changed, 4 insertions(+)

--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -2294,6 +2294,7 @@ void pci_msi_off(struct pci_dev *dev)
pci_write_config_word(dev, pos + PCI_MSIX_FLAGS, control);

int pci_set_dma_max_seg_size(struct pci_dev *dev, unsigned int size)
--- a/drivers/virtio/virtio_pci.c
+++ b/drivers/virtio/virtio_pci.c
@@ -636,6 +636,9 @@ static int __devinit virtio_pci_probe(st

+ /* Disable MSI/MSIX to bring device to a known good state. */
+ pci_msi_off(pci_dev);
/* enable the device */
err = pci_enable_device(pci_dev);
if (err)

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