From: Joerg Roedel <jroedel@suse.de>
To: Andy Lutomirski <luto@kernel.org>
Cc: linux-kernel@vger.kernel.org,
Christian Borntraeger <borntraeger@de.ibm.com>,
Cornelia Huck <cornelia.huck@de.ibm.com>,
Sebastian Ott <sebott@linux.vnet.ibm.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Christoph Hellwig <hch@lst.de>,
benh@kernel.crashing.org, KVM <kvm@vger.kernel.org>,
dwmw2@infradead.org, Martin Schwidefsky <schwidefsky@de.ibm.com>,
linux-s390 <linux-s390@vger.kernel.org>,
Andy Lutomirski <luto@amacapital.net>
Subject: Re: [PATCH 2/3] virtio_ring: Support DMA APIs
Date: Wed, 28 Oct 2015 11:06:50 +0900 [thread overview]
Message-ID: <20151028020650.GA18467@suse.de> (raw)
In-Reply-To: <6b42014d04258c706c7c43ae739efb30e32496b9.1445994839.git.luto@kernel.org>
Hi Andy,
On Tue, Oct 27, 2015 at 06:17:09PM -0700, Andy Lutomirski wrote:
> From: Andy Lutomirski <luto@amacapital.net>
>
> 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
next prev parent reply other threads:[~2015-10-28 2:06 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-28 1:17 [PATCH 0/3] virtio DMA API core stuff Andy Lutomirski
2015-10-28 1:17 ` [PATCH 1/3] virtio_net: Stop doing DMA from the stack Andy Lutomirski
2015-10-28 2:07 ` Joerg Roedel
2015-10-28 2:14 ` Andy Lutomirski
2015-10-28 1:17 ` [PATCH 2/3] virtio_ring: Support DMA APIs Andy Lutomirski
2015-10-28 2:06 ` Joerg Roedel [this message]
2015-10-28 2:13 ` Andy Lutomirski
2015-10-28 2:21 ` Joerg Roedel
2015-10-28 5:12 ` Andy Lutomirski
2015-10-28 2:27 ` Christian Borntraeger
2015-10-28 5:09 ` Andy Lutomirski
2015-10-28 1:17 ` [PATCH 3/3] virtio_pci: Use the DMA API Andy Lutomirski
2015-10-28 2:15 ` Joerg Roedel
2015-10-28 2:22 ` David Woodhouse
2015-10-28 2:50 ` Joerg Roedel
2015-10-28 2:25 ` Joerg Roedel
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