From: Catalin Marinas <catalin.marinas@arm•com>
To: Oliver Upton <oliver.upton@linux•dev>
Cc: kvmarm@lists•linux.dev, Marc Zyngier <maz@kernel•org>,
James Morse <james.morse@arm•com>,
Suzuki K Poulose <suzuki.poulose@arm•com>,
Zenghui Yu <yuzenghui@huawei•com>, Will Deacon <will@kernel•org>,
linux-arm-kernel@lists•infradead.org,
Darren Hart <darren@os•amperecomputing.com>,
D Scott Phillips <scott@os•amperecomputing.com>
Subject: Re: [PATCH 0/3] KVM: arm64: Work around Ampere1 erratum AC03_CPU_38
Date: Wed, 14 Jun 2023 17:57:55 +0100 [thread overview]
Message-ID: <ZInxk+75cYfP3N4S@arm.com> (raw)
In-Reply-To: <20230609220104.1836988-1-oliver.upton@linux.dev>
On Fri, Jun 09, 2023 at 10:01:01PM +0000, Oliver Upton wrote:
> Small series to work around a CPU erratum on AmpereOne. While the
> implementation does not advertise support for FEAT_HAFDBS (due to
> another erratum), the associated control bits do not have RES0 behavior
> as required by the architecture.
>
> Usage of HAFDBS at stage-1 is unaffected, since HA and HD are only
> enabled on implementations that advertise the feature. However, KVM
> relies on HA having RES0 semantics if the feature isn't implemented. The
> end result is that KVM enables a broken hardware access flag
> implementation that could lead to correctness issues.
Just curious, what's the correctness issue here? The access flag is
mostly indicative of which pages are old for swapping out/discarding.
It's not like the dirty state which would be dangerous if we get wrong.
--
Catalin
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next prev parent reply other threads:[~2023-06-14 16:58 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-09 22:01 [PATCH 0/3] KVM: arm64: Work around Ampere1 erratum AC03_CPU_38 Oliver Upton
2023-06-09 22:01 ` [PATCH 1/3] arm64: errata: Mitigate Ampere1 erratum AC03_CPU_38 at stage-2 Oliver Upton
2023-06-14 16:58 ` Catalin Marinas
2023-06-14 17:15 ` D Scott Phillips
2023-06-09 22:01 ` [PATCH 2/3] KVM: arm64: Refactor HFGxTR configuration into separate helpers Oliver Upton
2023-06-09 22:01 ` [PATCH 3/3] KVM: arm64: Prevent guests from enabling HA/HD on Ampere1 Oliver Upton
2023-06-14 16:57 ` Catalin Marinas [this message]
2023-06-14 23:06 ` [PATCH 0/3] KVM: arm64: Work around Ampere1 erratum AC03_CPU_38 Oliver Upton
2023-06-15 8:36 ` Catalin Marinas
2023-06-15 9:51 ` Marc Zyngier
2023-06-20 13:15 ` Oliver Upton
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