Re: Patch "KVM: arm64: nv: Add sanitising to VNCR-backed sysregs" has been added to the 6.8-stable tree

[Marc Zyngier <maz@kernel.org>]

On Mon, 03 Jun 2024 12:52:54 +0100,
Sasha Levin <sashal@kernel.org> wrote:
> 
> This is a note to let you know that I've just added the patch titled
> 
>     KVM: arm64: nv: Add sanitising to VNCR-backed sysregs
> 
> to the 6.8-stable tree which can be found at:
>     http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
> 
> The filename of the patch is:
>      kvm-arm64-nv-add-sanitising-to-vncr-backed-sysregs.patch
> and it can be found in the queue-6.8 subdirectory.
> 
> If you, or anyone else, feels it should not be added to the stable tree,
> please let <stable@vger.kernel.org> know about it.
> 
> 
> 
> commit fbb2bcdc458dd7db3860f85a06e98cc25904d20d
> Author: Marc Zyngier <maz@kernel.org>
> Date:   Wed Feb 14 13:18:04 2024 +0000
> 
>     KVM: arm64: nv: Add sanitising to VNCR-backed sysregs
>     
>     [ Upstream commit 888f0880702293096619b300150cd7e59fcd9743 ]
>     
>     VNCR-backed "registers" are actually only memory. Which means that
>     there is zero control over what the guest can write, and that it
>     is the hypervisor's job to actually sanitise the content of the
>     backing store. Yeah, this is fun.
>     
>     In order to preserve some form of sanity, add a repainting mechanism
>     that makes use of a per-VM set of RES0/RES1 masks, one pair per VNCR
>     register. These masks get applied on access to the backing store via
>     __vcpu_sys_reg(), ensuring that the state that is consumed by KVM is
>     correct.
>     
>     So far, nothing populates these masks, but stay tuned.
>     
>     Signed-off-by: Marc Zyngier <maz@kernel.org>
>     Reviewed-by: Joey Gouly <joey.gouly@arm.com>
>     Link: https://lore.kernel.org/r/20240214131827.2856277-4-maz@kernel.org
>     Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
>     Stable-dep-of: ce5d2448eb8f ("KVM: arm64: Destroy mpidr_data for 'late' vCPU creation")
>     Signed-off-by: Sasha Levin <sashal@kernel.org>

Please drop this. It serves no purpose on 6.8 aside from wasting
memory. If backporting ce5d2448eb8f is hard due to some conflicts,
we'll tackle it ourselves.

Thanks,

	M.

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