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

On Wed, Feb 03, 2021 at 01:49:22PM +0100, Christoph Hellwig wrote:

On Mon, Jan 18, 2021 at 12:44:58PM +0100, Martin Radev wrote:

quoted

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.

If you don't trust the hypervisor, what would this capability be in?

I suppose you mean this would need to be in the the guest kernel and
this protocol would depend on .. not-hypervisor and most certainly not
the virtio or any SR-IOV device. That removes a lot of options.

The one sensibile one (since folks will trust OEM vendors like Intel
or AMD to provide the memory encryption so they will also trust the
IOMMU - I hope?) - and they do have plans for that with their IOMMU
frameworks which will remove the need for SWIOTLB (I hope).

But that is not now, but in future.
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