Re: Re: [RFC PATCH V2 0/7] Do not read from descripto ring

[Yongji Xie]

On Fri, May 14, 2021 at 12:27 AM Stefan Hajnoczi <stefanha@xxxxxxxxxx> wrote:
>
> On Fri, Apr 23, 2021 at 04:09:35PM +0800, Jason Wang wrote:
> > Sometimes, the driver doesn't trust the device. This is usually
> > happens for the encrtpyed VM or VDUSE[1].
>
> Thanks for doing this.
>
> Can you describe the overall memory safety model that virtio drivers
> must follow? For example:
>
> - Driver-to-device buffers must be on dedicated pages to avoid
>   information leaks.
>
> - Driver-to-device buffers must be on dedicated pages to avoid memory
>   corruption.
>
> When I say "pages" I guess it's the IOMMU page size that matters?
>
> What is the memory access granularity of VDUSE?
>

Now we use PAGE_SIZE as the access granularity. I think it should be
safe to access the Driver-to-device buffers in VDUSE case because we
also use bounce-buffering mechanism like swiotlb does.

Thanks,
Yongji