[PATCH v6 virtio 02/11] virtio: allow caller to override device DMA mask in vp_modern

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To add a bit of vendor flexibility with various virtio based devices,
allow the caller to specify a different DMA mask.  This adds a dma_mask
field to struct virtio_pci_modern_device.  If defined by the driver,
this mask will be used in a call to dma_set_mask_and_coherent() instead
of the traditional DMA_BIT_MASK(64).  This allows limiting the DMA space
on vendor devices with address limitations.

Signed-off-by: Shannon Nelson <shannon.nelson@xxxxxxx>
Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
 drivers/virtio/virtio_pci_modern_dev.c | 3 ++-
 include/linux/virtio_pci_modern.h      | 3 +++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/virtio/virtio_pci_modern_dev.c b/drivers/virtio/virtio_pci_modern_dev.c
index 9b2d6614de67..aad7d9296e77 100644
--- a/drivers/virtio/virtio_pci_modern_dev.c
+++ b/drivers/virtio/virtio_pci_modern_dev.c
@@ -268,7 +268,8 @@ int vp_modern_probe(struct virtio_pci_modern_device *mdev)
 		return -EINVAL;
-	err = dma_set_mask_and_coherent(&pci_dev->dev, DMA_BIT_MASK(64));
+	err = dma_set_mask_and_coherent(&pci_dev->dev,
+					mdev->dma_mask ? : DMA_BIT_MASK(64));
 	if (err)
 		err = dma_set_mask_and_coherent(&pci_dev->dev,
diff --git a/include/linux/virtio_pci_modern.h b/include/linux/virtio_pci_modern.h
index e7b1db1dd0bb..067ac1d789bc 100644
--- a/include/linux/virtio_pci_modern.h
+++ b/include/linux/virtio_pci_modern.h
@@ -41,6 +41,9 @@ struct virtio_pci_modern_device {
 	/* optional check for vendor virtio device, returns dev_id or -ERRNO */
 	int (*device_id_check)(struct pci_dev *pdev);
+	/* optional mask for devices with limited DMA space */
+	u64 dma_mask;

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