Re: [PATCH stable 6.1.y 1/2] KVM: arm64: Prevent the donation of no-map pages

[Marc Zyngier]

On Wed, 20 Sep 2023 20:27:28 +0100,
Suraj Jitindar Singh <surajjs@xxxxxxxxxx> wrote:
> 
> From: Quentin Perret <qperret@xxxxxxxxxx>
> 
> commit 43c1ff8b75011bc3e3e923adf31ba815864a2494 upstream.
> 
> Memory regions marked as "no-map" in the host device-tree routinely
> include TrustZone carev-outs and DMA pools. Although donating such pages
> to the hypervisor may not breach confidentiality, it could be used to
> corrupt its state in uncontrollable ways. To prevent this, let's block
> host-initiated memory transitions targeting "no-map" pages altogether in
> nVHE protected mode as there should be no valid reason to do this in
> current operation.
> 
> Thankfully, the pKVM EL2 hypervisor has a full copy of the host's list
> of memblock regions, so we can easily check for the presence of the
> MEMBLOCK_NOMAP flag on a region containing pages being donated from the
> host.
> 
> Reviewed-by: Philippe Mathieu-Daudé <philmd@xxxxxxxxxx>
> Tested-by: Vincent Donnefort <vdonnefort@xxxxxxxxxx>
> Signed-off-by: Quentin Perret <qperret@xxxxxxxxxx>
> Signed-off-by: Will Deacon <will@xxxxxxxxxx>
> Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
> Link: https://lore.kernel.org/r/20221110190259.26861-8-will@xxxxxxxxxx
> [ bp: clean ]

What is this?

> Signed-off-by: Suraj Jitindar Singh <surajjs@xxxxxxxxxx>

What is the rationale for backporting this? It wasn't tagged as Cc: to
stable for a reason: pKVM isn't functional upstream, and won't be for
the next couple of cycles *at least*.

So at it stands, I'm against such a backport.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.