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From: Oliver Upton <oliver.upton@linux.dev>
To: Marc Zyngier <maz@kernel.org>
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>,
	Zenghui Yu <yuzenghui@huawei.com>,
	Peter Maydell <peter.maydell@linaro.org>, stable@vger.kernel.org
Subject: Re: [PATCH 1/3] KVM: arm64: Make ID_PFR1_EL1.GIC writable
Message-ID: <aPiBH1_WZicoE7Od@linux.dev>
References: <20251013083207.518998-1-maz@kernel.org>
 <20251013083207.518998-2-maz@kernel.org>
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Hey,

On Mon, Oct 13, 2025 at 09:32:05AM +0100, Marc Zyngier wrote:
> Similarly to ID_AA64PFR0_EL1.GIC, relax ID_PFR1_EL1.GIC to be writable.

This looks fine to me, although I do wonder if we should just allow
userspace to write whatever value it wants to the 32-bit ID registers
and be done with it.

Nowhere do we use a 32-bit ID register value as a condition for trap
configuration / emulation, so even if the VMM lies to the guest it
shouldn't trip up KVM.

Thanks,
Oliver