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authorWill Deacon <will.deacon@arm.com>2016-09-14 17:33:26 +0100
committerMichael S. Tsirkin <mst@redhat.com>2016-10-31 00:21:39 +0200
commita0be1db4304f51c99af6b6e515549794182a94df (patch)
treef21a49bccbc96339dd0037ed6facec7079fe2006
parenta909d3e636995ba7c349e2ca5dbb528154d4ac30 (diff)
virtio_pci: Limit DMA mask to 44 bits for legacy virtio devices
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: stable@vger.kernel.org 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>
-rw-r--r--drivers/virtio/virtio_pci_legacy.c16
1 files changed, 12 insertions, 4 deletions
diff --git a/drivers/virtio/virtio_pci_legacy.c b/drivers/virtio/virtio_pci_legacy.c
index 8c4e61783441..6d9e5173d5fa 100644
--- a/drivers/virtio/virtio_pci_legacy.c
+++ b/drivers/virtio/virtio_pci_legacy.c
@@ -212,10 +212,18 @@ int virtio_pci_legacy_probe(struct virtio_pci_device *vp_dev)
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");