| From a0be1db4304f51c99af6b6e515549794182a94df Mon Sep 17 00:00:00 2001 |
| From: Will Deacon <will.deacon@arm.com> |
| Date: Wed, 14 Sep 2016 17:33:26 +0100 |
| Subject: virtio_pci: Limit DMA mask to 44 bits for legacy virtio devices |
| |
| From: Will Deacon <will.deacon@arm.com> |
| |
| commit a0be1db4304f51c99af6b6e515549794182a94df upstream. |
| |
| Legacy virtio defines the virtqueue base using a 32-bit PFN field, with |
| a read-only register indicating a fixed page size of 4k. |
| |
| This can cause problems for DMA allocators that allocate top down from |
| the DMA mask, which is set to 64 bits. In this case, the addresses are |
| silently truncated to 44-bit, leading to IOMMU faults, failure to read |
| from the queue or data corruption. |
| |
| This patch restricts the coherent DMA mask for legacy PCI virtio devices |
| to 44 bits, which matches the specification. |
| |
| Cc: Andy Lutomirski <luto@kernel.org> |
| Cc: Michael S. Tsirkin <mst@redhat.com> |
| Cc: Benjamin Serebrin <serebrin@google.com> |
| Signed-off-by: Will Deacon <will.deacon@arm.com> |
| Signed-off-by: Michael S. Tsirkin <mst@redhat.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| drivers/virtio/virtio_pci_legacy.c | 16 ++++++++++++---- |
| 1 file changed, 12 insertions(+), 4 deletions(-) |
| |
| --- a/drivers/virtio/virtio_pci_legacy.c |
| +++ b/drivers/virtio/virtio_pci_legacy.c |
| @@ -212,10 +212,18 @@ int virtio_pci_legacy_probe(struct virti |
| return -ENODEV; |
| } |
| |
| - rc = dma_set_mask_and_coherent(&pci_dev->dev, DMA_BIT_MASK(64)); |
| - if (rc) |
| - rc = dma_set_mask_and_coherent(&pci_dev->dev, |
| - DMA_BIT_MASK(32)); |
| + rc = dma_set_mask(&pci_dev->dev, DMA_BIT_MASK(64)); |
| + if (rc) { |
| + rc = dma_set_mask_and_coherent(&pci_dev->dev, DMA_BIT_MASK(32)); |
| + } else { |
| + /* |
| + * The virtio ring base address is expressed as a 32-bit PFN, |
| + * with a page size of 1 << VIRTIO_PCI_QUEUE_ADDR_SHIFT. |
| + */ |
| + dma_set_coherent_mask(&pci_dev->dev, |
| + DMA_BIT_MASK(32 + VIRTIO_PCI_QUEUE_ADDR_SHIFT)); |
| + } |
| + |
| if (rc) |
| dev_warn(&pci_dev->dev, "Failed to enable 64-bit or 32-bit DMA. Trying to continue, but this might not work.\n"); |
| |