From: Marc Zyngier <maz@kernel.org>
To: Cornelia Huck <cohuck@redhat.com>
Cc: kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
kvm@vger.kernel.org, Joey Gouly <joey.gouly@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Oliver Upton <oliver.upton@linux.dev>,
Zenghui Yu <yuzenghui@huawei.com>, Will Deacon <will@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>
Subject: Re: [PATCH 6/7] KVM: arm64: Expose FEAT_RASv1p1 in a canonical manner
Date: Mon, 21 Jul 2025 13:55:37 +0100 [thread overview]
Message-ID: <86o6td8zzq.wl-maz@kernel.org> (raw)
In-Reply-To: <87seip67xz.fsf@redhat.com>
On Mon, 21 Jul 2025 13:32:08 +0100,
Cornelia Huck <cohuck@redhat.com> wrote:
>
> On Mon, Jul 21 2025, Marc Zyngier <maz@kernel.org> wrote:
>
> > If we have RASv1p1 on the host, advertise it to the guest in the
> > "canonical way", by setting ID_AA64PFR0_EL1 to V1P1, rather than
> > the convoluted RAS+RAS_frac method.
>
> Don't the two methods have slightly different semantics with RAS == V1P1
> possibly implying FEAT_DoubleFault, and RAS+RAS_frac not?
Ah, that's an interesting point -- I definitely had glanced over that.
But I'm not sure a guest can actually distinguish between these two
configurations, given that FEAT_DoubleFault is essentially an EL3
feature (as indicated in the RAS == V1P1 section, and further
confirmed in R_GRJVN), making it invisible to the guest.
FEAT_DoubleFault2 is, on the contrary, totally visible from the guest,
and independent of EL3.
Does this make sense to you?
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
next prev parent reply other threads:[~2025-07-21 12:55 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-07-21 10:19 [PATCH 0/7] KVM: arm64: FEAT_RASv1p1 support and RAS selection Marc Zyngier
2025-07-21 10:19 ` [PATCH 1/7] arm64: Add capability denoting FEAT_RASv1p1 Marc Zyngier
2025-07-21 13:52 ` Catalin Marinas
2025-07-21 10:19 ` [PATCH 2/7] KVM: arm64: Filter out HCR_EL2 bits when running in hypervisor context Marc Zyngier
2025-07-21 10:19 ` [PATCH 3/7] KVM: arm64: Make RAS registers UNDEF when RAS isn't advertised Marc Zyngier
2025-07-21 10:19 ` [PATCH 4/7] KVM: arm64: Handle RASv1p1 registers Marc Zyngier
2025-07-21 13:08 ` Marc Zyngier
2025-07-21 10:19 ` [PATCH 5/7] KVM: arm64: Ignore HCR_EL2.FIEN set by L1 guest's EL2 Marc Zyngier
2025-07-21 10:19 ` [PATCH 6/7] KVM: arm64: Expose FEAT_RASv1p1 in a canonical manner Marc Zyngier
2025-07-21 12:32 ` Cornelia Huck
2025-07-21 12:55 ` Marc Zyngier [this message]
2025-07-21 13:12 ` Cornelia Huck
2025-07-21 13:33 ` Marc Zyngier
2025-07-21 10:19 ` [PATCH 7/7] KVM: arm64: Make ID_AA64PFR0_EL1.RAS writable Marc Zyngier
2025-07-21 22:24 ` (subset) [PATCH 0/7] KVM: arm64: FEAT_RASv1p1 support and RAS selection Oliver Upton
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