linux-kernel - Re: [PATCH 0/4] KVM: arm64: Fix CPU resume/on with pKVM

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Message-ID: <Y9qZ5XoXW1XQ70eE@google.com>
Date:   Wed, 1 Feb 2023 16:57:09 +0000
From:   Quentin Perret <qperret@...gle.com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Mark Brown <broonie@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kvmarm@...ts.linux.dev, kvmarm@...ts.cs.columbia.edu,
        kernel-team@...roid.com
Subject: Re: [PATCH 0/4] KVM: arm64: Fix CPU resume/on with pKVM

On Wednesday 01 Feb 2023 at 14:48:03 (+0000), Marc Zyngier wrote:
> On Wed, 01 Feb 2023 10:37:50 +0000,
> Quentin Perret <qperret@...gle.com> wrote:
> > 
> > When using pKVM, we do not reset the EL2 exception vectors back to the
> > stubs for e.g. Power Management or CPU hotplug as we normally do in KVM.
> > As consequence, the initialisation perfomed by __finalise_el2 is missing
> > on e.g. the CPU_RESUME path with pKVM, hence leaving certain registers
> > in an incorrect state.
> > 
> > One such example is ZCR_EL2 which remains configured with SVE traps
> > enabled. And so using SVE on a CPU that has gone through a hotplug
> > off/on cycle leads to a hyp panic. Not good.
> > 
> > This series fixes this by macroizing the first half of __finalise_el2
> > (that is, the part that is not specific to VHE) to allow its re-use
> > from pKVM's PSCI relay.
> 
> For the series:
> 
> Reviewed-by: Marc Zyngier <maz@...nel.org>
> 
> I think it might be a bit late to send this as fixes for 6.2 (my
> latest pull request for kvmarm-fixes-6.2-3 is still in limbo), so I'd
> suggest we take it for 6.3.

Works for me.

> How do you want to deal with the backports? None of the patches have a
> Cc: stable, and only the last one has a Fixes: tag, but cannot be
> applied standalone.

Right, I wasn't sure what was best -- the first patches aren't really
fixing anything per se but yeah, we kinda need them...

Happy to re-post a version with the same 'Fixes:' tag on all patches and
'Cc: stable' everywhere if that makes things easier. Wdyt?

Cheers,
Quentin