linux-kernel - Re: [PATCH 3/4] KVM: arm64: Fix FFR offset calculation for pKVM host state save and restore

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Message-ID: <af6fd3c0-f411-4f33-aa8a-885873a74c73@sirena.org.uk>
Date: Wed, 5 Jun 2024 14:17:36 +0100
From: Mark Brown <broonie@...nel.org>
To: Fuad Tabba <tabba@...gle.com>
Cc: Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
	Oliver Upton <oliver.upton@...ux.dev>,
	James Morse <james.morse@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	kvmarm@...ts.linux.dev
Subject: Re: [PATCH 3/4] KVM: arm64: Fix FFR offset calculation for pKVM host
 state save and restore

On Wed, Jun 05, 2024 at 01:12:34PM +0100, Fuad Tabba wrote:

> If my understanding of the spec is correct (which more often than not
> it isn't), I don't think we have an issue as long as we use the same
> value in the offset on saving/restoring, and that that value
> represents the maximum possible value.

Yes, we could also correct the issue by switching to use the system
enumerated maximum but that still leaves us setting one value and then
immediately assuming a different value.  Reading the actual VL from the
hardware makes the code more obviously self consistent.

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