4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Robin Murphy <robin.murphy@xxxxxxx>
commit f7f6634d23830ff74335734fbdb28ea109c1f349 upstream.
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
a0be1db4304f ("virtio_pci: Limit DMA mask to 44 bits for legacy virtio
devices").
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
Reported-by: Jean-Philippe Brucker <jean-philippe.brucker@xxxxxxx>
Fixes: b42111382f0e ("virtio_mmio: Use the DMA API if enabled")
Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx>
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/virtio/virtio_mmio.c | 20 +++++++++++++++++++-
1 file changed, 19 insertions(+), 1 deletion(-)
--- a/drivers/virtio/virtio_mmio.c
+++ b/drivers/virtio/virtio_mmio.c
@@ -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>
@@ -497,6 +498,7 @@ static int virtio_mmio_probe(struct plat
struct virtio_mmio_device *vm_dev;
struct resource *mem;
unsigned long magic;
+ int rc;
mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
if (!mem)
@@ -545,9 +547,25 @@ static int virtio_mmio_probe(struct plat
}
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);
--
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