[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [early RFC] ARM PCI Passthrough design document
Hi Stefano, On 02/13/2017 07:59 PM, Stefano Stabellini wrote: > On Mon, 13 Feb 2017, Julien Grall wrote: >> Hi Stefano, >> >> On 10/02/17 01:01, Stefano Stabellini wrote: >>> On Fri, 3 Feb 2017, Edgar E. Iglesias wrote: >>>> A possible hack could be to allocate a chunk of DDR dedicated for PCI DMA. >>>> PCI DMA devs could be locked in to only be able to access this mem + MSI >>>> doorbell. >>>> Guests can still screw each other up but at least it becomes harder to >>>> read/write directly from each others OS memory. >>>> It may not be worth the effort though.... >>> >>> Actually, we do have the swiotlb in Dom0, which can be used to bounce >>> DMA requests over a buffer that has been previously setup to be DMA safe >>> using an hypercall. That is how the swiotlb is used on x86. On ARM it is >>> used to issue cache flushes via hypercall, but it could be adapted to do >>> both. It would degrade performance, due to the additional memcpy, but it >>> would work, I believe. >> >> A while ago, Globallogic suggested to use direct memory mapping for the guest >> to allow guest using DMA on platform not supporting SMMU. >> >> I believe we can use the same trick on platform where SMMUs can not >> distinguish PCI devices. > > Yes, that would work, but only on platforms with a very limited number > of guests. However, it might still be a very common use-case on a > platform such as the Zynq MPSoC. Can you explain why you think this could only work with limited number of guests? Cheers, -- Julien Grall _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx https://lists.xen.org/xen-devel
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