Re: [Xen-devel] [PATCH RFC 0/3] Xen on Virtio
From: David Vrabel
Date: Mon Dec 14 2015 - 09:00:18 EST
On 07/12/15 16:19, Stefano Stabellini wrote:
> Hi all,
> this patch series introduces support for running Linux on top of Xen
> inside a virtual machine with virtio devices (nested virt scenario).
> The problem is that Linux virtio drivers use virt_to_phys to get the
> guest pseudo-physical addresses to pass to the backend, which doesn't
> work as expected on Xen.
> Switching the virtio drivers to the dma APIs (dma_alloc_coherent,
> dma_map/unmap_single and dma_map/unmap_sg) would solve the problem, as
> Xen support in Linux provides an implementation of the dma API which
> takes care of the additional address conversions. However using the dma
> API would increase the complexity of the non-Xen case too. We would also
> need to keep track of the physical or virtual address in addition to the
> dma address for each vring_desc to be able to free the memory in
> detach_buf (see patch #3).
> Instead this series adds few obvious checks to perform address
> translations in a couple of key places, without changing non-Xen code
> paths. You are welcome to suggest improvements or alternative
Andy Lutomirski also looked at this. Andy what happened to this work?
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