linux-kernel - Re: [PATCH] KVM: arm64: Bump KVM_VCPU_MAX

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Message-ID: <86a5dkvh9o.wl-maz@kernel.org>
Date: Wed, 27 Nov 2024 15:16:35 +0000
From: Marc Zyngier <maz@...nel.org>
To: Steven Price <steven.price@....com>
Cc: Catalin Marinas <catalin.marinas@....com>,
	Oliver Upton <oliver.upton@...ux.dev>,
	Will Deacon <will@...nel.org>,
	Joey Gouly <joey.gouly@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Zenghui Yu <yuzenghui@...wei.com>,
	kvmarm@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: arm64: Bump KVM_VCPU_MAX_FEATURES

On Wed, 27 Nov 2024 14:56:31 +0000,
Steven Price <steven.price@....com> wrote:
> 
> When the KVM_ARM_VCPU_HAS_EL2 define was added, the value of
> KVM_VCPU_MAX_FEATURES wasn't incremented, so that feature has never been
> in the KVM_VCPU_VALID_FEATURES bit mask. This means the HAS_EL2 feature
> will never be exposed to user space even if the system supports it.
> 
> Fixes: 89b0e7de3451 ("KVM: arm64: nv: Introduce nested virtualization VCPU feature")
> Signed-off-by: Steven Price <steven.price@....com>
> ---
> I might be missing something, and it's possible that
> KVM_ARM_VCPU_HAS_EL2 is deliberately not exposed yet.

This is on purpose. I'm not planning to enable EL2 support until it is
ready.

> However I'm
> working on v6 of the host CCA series and as part of that want to add a
> new feature but and bump KVM_VCPU_MAX_FEATURES up to 9.

Well, I guess that defines some ordering then! :D

	M.

-- 
Without deviation from the norm, progress is not possible.