linux-kernel - Re: [PATCH v1 1/8] virtio: Force only split mode with protected guest

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Message-ID: <9d6bc785-9613-a2e8-f78f-4547747a331d@linux.intel.com>
Date:   Thu, 3 Jun 2021 06:55:08 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     Jason Wang <jasowang@...hat.com>, mst@...hat.com
Cc:     virtualization@...ts.linux-foundation.org, hch@....de,
        m.szyprowski@...sung.com, robin.murphy@....com,
        iommu@...ts.linux-foundation.org, x86@...nel.org,
        sathyanarayanan.kuppuswamy@...ux.intel.com, jpoimboe@...hat.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/8] virtio: Force only split mode with protected guest


> Ok, but what I meant is this, if we don't read from the descriptor 
> ring, and validate all the other metadata supplied by the device (used 
> id and len). Then there should be no way for the device to suppress 
> the dma flags to write to the indirect descriptor table.
>
> Or do you have an example how it can do that?

I don't. If you can validate everything it's probably ok

The only drawback is even more code to audit and test.

-Andi