Re: [PATCH 2/3] virtio_ring: Support DMA APIs

[Joerg Roedel]

Hi Andy,

On Tue, Oct 27, 2015 at 06:17:09PM -0700, Andy Lutomirski wrote:
> From: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
> 
> virtio_ring currently sends the device (usually a hypervisor)
> physical addresses of its I/O buffers.  This is okay when DMA
> addresses and physical addresses are the same thing, but this isn't
> always the case.  For example, this never works on Xen guests, and
> it is likely to fail if a physical "virtio" device ever ends up
> behind an IOMMU or swiotlb.

The overall code looks good, but I havn't seen and dma_sync* calls.
When swiotlb=force is in use this would break.

> +		vq->vring.desc[head].addr = cpu_to_virtio64(_vq->vdev, vring_map_single(
> +			vq,
> +			desc, total_sg * sizeof(struct vring_desc),
> +			DMA_TO_DEVICE));

Nit: I think readability could be improved here by using a temporary
variable for the return value of vring_map_single().


	Joerg

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/