From: Oliver Upton <oupton@google.com>
To: Marc Zyngier <maz@kernel.org>
Cc: kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org, kernel@android.com,
stable@vger.kernel.org
Subject: Re: [PATCH] KVM: arm64: vgic-v3: Consistently populate ID_AA64PFR0_EL1.GIC
Date: Wed, 4 May 2022 03:32:56 +0000 [thread overview]
Message-ID: <YnHz6Cw5ONR2e+KA@google.com> (raw)
In-Reply-To: <20220503211424.3375263-1-maz@kernel.org>
On Tue, May 03, 2022 at 10:14:24PM +0100, Marc Zyngier wrote:
> When adding support for the slightly wonky Apple M1, we had to
> populate ID_AA64PFR0_EL1.GIC==1 to present something to the guest,
> as the HW itself doesn't advertise the feature.
>
> However, we gated this on the in-kernel irqchip being created.
> This causes some trouble for QEMU, which snapshots the state of
> the registers before creating a virtual GIC, and then tries to
> restore these registers once the GIC has been created. Obviously,
> between the two stages, ID_AA64PFR0_EL1.GIC has changed value,
> and the write fails.
>
> The fix is to actually emulate the HW, and always populate the
> field if the HW is capable of it.
>
> Fixes: 562e530fd770 ("KVM: arm64: Force ID_AA64PFR0_EL1.GIC=1 when exposing a virtual GICv3")
> Cc: stable@vger.kernel.org
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> Reported-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Oliver Upton <oupton@google.com>
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prev parent reply other threads:[~2022-05-04 3:34 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-03 21:14 [PATCH] KVM: arm64: vgic-v3: Consistently populate ID_AA64PFR0_EL1.GIC Marc Zyngier
2022-05-04 3:32 ` Oliver Upton [this message]
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