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Re: [Qemu-devel] [PATCH v5 07/11] vfio: Add guest side IOMMU support


From: Paolo Bonzini
Subject: Re: [Qemu-devel] [PATCH v5 07/11] vfio: Add guest side IOMMU support
Date: Fri, 21 Mar 2014 15:23:06 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0

Il 21/03/2014 15:17, Alex Williamson ha scritto:
> > Is this possible?  Assuming len is initially a power-of-2, would the
> > translate function change it?  Maybe worth a comment to explain.


Oh. address_space_translate() actually changes @len to min(len,
TARGET_PAGE_SIZE) and TARGET_PAGE_SIZE is hardcoded to 4K. So far it was ok
but lately I have been implementing a huge DMA window (plus one
sPAPRTCETable and one VFIOGuestIOMMU objects) which currently operates with
16MB pages (can do 64K pages too) and now this "granularity incompatible"
is happening.

I disabled that check but I need to think of better fix...

Adding Paolo to cc, may be he picks the context and gives good piece of
advise :)

I think that "if" in address_space_translate should be restricted to Xen, since that's what it was added for.

Paolo



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