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From:   Yongji Xie <xieyongji@bytedance.com>
Date:   Fri, 14 May 2021 14:06:38 +0800
Message-ID: <CACycT3v-2naEaXEtPqaKcGz8qpfnmp4VzrHefqLNhO=9=57jdQ@mail.gmail.com>
Subject: Re: Re: [RFC PATCH V2 0/7] Do not read from descripto ring
To:     Stefan Hajnoczi <stefanha@redhat.com>
Cc:     Jason Wang <jasowang@redhat.com>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        virtualization@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org, file@sect.tu-berlin.de,
        ashish.kalra@amd.com, konrad.wilk@oracle.com, kvm@vger.kernel.org,
        Christoph Hellwig <hch@infradead.org>
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On Fri, May 14, 2021 at 12:27 AM Stefan Hajnoczi <stefanha@redhat.com> 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