linux-kernel - Re: [PATCH 6.12 8/8] KVM: arm64: Eagerly switch ZCR

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Message-ID: <83ba4e5b-7700-4527-8376-2c60507bd0d7@sirena.org.uk>
Date: Wed, 19 Mar 2025 13:02:30 +0000
From: Mark Brown <broonie@...nel.org>
To: Mark Rutland <mark.rutland@....com>
Cc: Marc Zyngier <maz@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Gavin Shan <gshan@...hat.com>,
	Oliver Upton <oliver.upton@...ux.dev>,
	Joey Gouly <joey.gouly@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>, linux-arm-kernel@...ts.infradead.org,
	kvmarm@...ts.linux.dev, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org, Fuad Tabba <tabba@...gle.com>
Subject: Re: [PATCH 6.12 8/8] KVM: arm64: Eagerly switch ZCR_EL{1,2}

On Wed, Mar 19, 2025 at 10:20:11AM +0000, Mark Rutland wrote:
> On Wed, Mar 19, 2025 at 09:15:54AM +0000, Marc Zyngier wrote:

> > The result is that this change is turning a perfectly valid HYP VA
> > into... something. Odds are that the masking/patching will not mess up
> > the address, but this is completely buggy anyway. In general,
> > kern_hyp_va() is not an idempotent operation.

> IIUC today it *happens* to be idempotent, but as you say that is not
> guaranteed to remain the case, and this is definitely a logical bug.

I think so, yes.  I suspect the idempotency confused me.

> > Greg, it may be more prudent to unstage this series from 6.12-stable
> > until we know for sure this is the only problem.

> As above, likewise with the v6.13 version.

Yes, please unstage these.  I'll send out new versions.

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