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
a0be1db4304f ("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: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Fixes: b42111382f0e ("virtio_mmio: Use the DMA API if enabled")
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
index d47a2fcef818f3cea1ce7f09160061b3c8d2f0a6..c71fde5fe835c48d1ce4611b29108f8cf7fb44f3 100644 (file)
--- 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>
@@ -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);