Commit f7f6634d authored by Robin Murphy's avatar Robin Murphy Committed by Michael S. Tsirkin

virtio_mmio: Set DMA masks appropriately

Once DMA API usage is enabled, it becomes apparent that virtio-mmio is
inadvertently relying on the default 32-bit DMA mask, which leads to
problems like rapidly exhausting SWIOTLB bounce buffers.

Ensure that we set the appropriate 64-bit DMA mask whenever possible,
with the coherent mask suitably limited for the legacy vring as per
a0be1db4 ("virtio_pci: Limit DMA mask to 44 bits for legacy virtio

Cc: Andy Lutomirski <>
Cc: Michael S. Tsirkin <>
Reported-by: default avatarJean-Philippe Brucker <>
Fixes: b4211138 ("virtio_mmio: Use the DMA API if enabled")
Signed-off-by: Robin Murphy's avatarRobin Murphy <>
Signed-off-by: Michael S. Tsirkin's avatarMichael S. Tsirkin <>
parent 0516ffd8
......@@ -59,6 +59,7 @@
#define pr_fmt(fmt) "virtio-mmio: " fmt
#include <linux/acpi.h>
#include <linux/dma-mapping.h>
#include <linux/highmem.h>
#include <linux/interrupt.h>
#include <linux/io.h>
......@@ -498,6 +499,7 @@ static int virtio_mmio_probe(struct platform_device *pdev)
struct virtio_mmio_device *vm_dev;
struct resource *mem;
unsigned long magic;
int rc;
mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
if (!mem)
......@@ -547,9 +549,25 @@ static int virtio_mmio_probe(struct platform_device *pdev)
vm_dev-> = readl(vm_dev->base + VIRTIO_MMIO_VENDOR_ID);
if (vm_dev->version == 1)
if (vm_dev->version == 1) {
writel(PAGE_SIZE, vm_dev->base + VIRTIO_MMIO_GUEST_PAGE_SIZE);
rc = dma_set_mask(&pdev->dev, DMA_BIT_MASK(64));
* In the legacy case, ensure our coherently-allocated virtio
* ring will be at an address expressable as a 32-bit PFN.
if (!rc)
} else {
rc = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
if (rc)
rc = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
if (rc)
dev_warn(&pdev->dev, "Failed to enable 64-bit or 32-bit DMA. Trying to continue, but this might not work.\n");
platform_set_drvdata(pdev, vm_dev);
return register_virtio_device(&vm_dev->vdev);
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