linux-kernel - Re: [PATCH] swiotlb: Validate bounce size in the sync/unmap path

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Date:   Wed, 3 Feb 2021 13:49:22 +0100
From:   Christoph Hellwig <hch@....de>
To:     Martin Radev <martin.b.radev@...il.com>
Cc:     Christoph Hellwig <hch@....de>, konrad.wilk@...cle.com,
        m.szyprowski@...sung.com, robin.murphy@....com,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        joro@...tes.org, kirill.shutemov@...ux.intel.com,
        thomas.lendacky@....com, robert.buhren@...t.tu-berlin.de,
        file@...t.tu-berlin.de, mathias.morbitzer@...ec.fraunhofer.de,
        virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org
Subject: Re: [PATCH] swiotlb: Validate bounce size in the sync/unmap path

On Mon, Jan 18, 2021 at 12:44:58PM +0100, Martin Radev wrote:
> Your comment makes sense but then that would require the cooperation
> of these vendors and the cloud providers to agree on something meaningful.
> I am also not sure whether the end result would be better than hardening
> this interface to catch corruption. There is already some validation in
> unmap path anyway.

So what?  If you guys want to provide a new capability you'll have to do
work.  And designing a new protocol based around the fact that the
hardware/hypervisor is not trusted and a copy is always required makes
a lot of more sense than throwing in band aids all over the place.