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

Cc: Andy Lutomirski <luto@kernel.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Reported-by: default avatarJean-Philippe Brucker <jean-philippe.brucker@arm.com>
Fixes: b4211138 ("virtio_mmio: Use the DMA API if enabled")
Signed-off-by: default avatarRobin Murphy <robin.murphy@arm.com>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent 0516ffd8

drivers/virtio/virtio_mmio.c

+19 −1
Original line number Diff line number Diff line
@@ -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->vdev.id.vendor = 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)

			dma_set_coherent_mask(&pdev->dev,

					      DMA_BIT_MASK(32 + PAGE_SHIFT));

	} 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);