linux-kernel - Re: [PATCH v4 1/3] KVM: arm64: Disable fields that KVM doesn't know how to handle in ID_AA64PFR1

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Message-ID: <ZpixhBjsqhWTpEQH@linux.dev>
Date: Wed, 17 Jul 2024 23:09:08 -0700
From: Oliver Upton <oliver.upton@...ux.dev>
To: Shaoqin Huang <shahuang@...hat.com>
Cc: Marc Zyngier <maz@...nel.org>, kvmarm@...ts.linux.dev,
	Mark Brown <broonie@...nel.org>, Eric Auger <eauger@...hat.com>,
	Sebastian Ott <sebott@...hat.com>,
	Cornelia Huck <cohuck@...hat.com>,
	James Morse <james.morse@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Zenghui Yu <yuzenghui@...wei.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/3] KVM: arm64: Disable fields that KVM doesn't know
 how to handle in ID_AA64PFR1_EL1

Hi Shaoqin,

On Wed, Jul 17, 2024 at 11:50:14PM -0400, Shaoqin Huang wrote:
> For some of the fields in the ID_AA64PFR1_EL1 register, KVM doesn't know
> how to handle them right now. So explicitly disable them in the register
> accessor, then those fields value will be masked to 0 even if on the
> hardware the field value is 1.

It is probably important to note that the only reason this is safe to do
from a UAPI POV is that read_sanitised_ftr_reg() doesn't yet return a
nonzero value for any of these fields.

-- 
Thanks,
Oliver