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SubjectRe: [PATCH] vfio iommu type1: Bypass the vma permission check in vfio_pin_pages_remote()
On Wed, Nov 25, 2020 at 01:05:25AM +0000, Justin He wrote:
> > I'd appreciate if you could explain why vfio needs to dma map some
> > PROT_NONE
>
> Virtiofs will map a PROT_NONE cache window region firstly, then remap the sub
> region of that cache window with read or write permission. I guess this might
> be an security concern. Just CC virtiofs expert Stefan to answer it more accurately.

Yep. Since my previous sentence was cut off, I'll rephrase: I was thinking
whether qemu can do vfio maps only until it remaps the PROT_NONE regions into
PROT_READ|PROT_WRITE ones, rather than trying to map dma pages upon PROT_NONE.

Thanks,

--
Peter Xu

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