On Tue, Oct 27, 2015 at 7:06 PM, Joerg Roedel <jroedel@xxxxxxx> wrote: > 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)); > Are you talking about a dma_sync call on the descriptor ring itself? Isn't dma_alloc_coherent supposed to make that unnecessary? I should move the allocation into the virtqueue code. The docs suggest that I might need to "flush the processor's write buffers before telling devices to read that memory". I'm not sure how to do that. > Nit: I think readability could be improved here by using a temporary > variable for the return value of vring_map_single(). > I'll do something like that for v2. --Andy -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
