Date: Tue, 09 Jun 2026 11:33:09 +0100
Message-ID: <86fr2wt34q.wl-maz@kernel.org>
From: Marc Zyngier <maz@kernel.org>
To: Hyunwoo Kim <imv4bel@gmail.com>
Cc: gregkh@linuxfoundation.org,
	stable@vger.kernel.org,
	oupton@kernel.org
Subject: Re: [PATCH 6.12.y] KVM: arm64: Take the SRCU lock for page table walks in fault injection and AT emulation
In-Reply-To: <aifnUC7gmeniiYPv@v4bel>
References: <aifnUC7gmeniiYPv@v4bel>
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On Tue, 09 Jun 2026 11:13:36 +0100,
Hyunwoo Kim <imv4bel@gmail.com> wrote:
> 
> [ Upstream commit f2ca45b50d4216c9cc7ffabf50d9ad1932209251 ]
> 
> walk_s1() and kvm_walk_nested_s2() expect to be called while holding
> kvm->srcu to guard against memslot changes. While this is generally
> the case, __kvm_at_s12() and __kvm_find_s1_desc_level() call into the
> respective walkers without taking kvm->srcu.
> 
> Fix by acquiring kvm->srcu prior to the table walk in both instances.
> 
> Cc: stable@vger.kernel.org
> Fixes: 50f77dc87f13 ("KVM: arm64: Populate level on S1PTW SEA injection")
> Fixes: be04cebf3e78 ("KVM: arm64: nv: Add emulation of AT S12E{0,1}{R,W}")
> Suggested-by: Oliver Upton <oupton@kernel.org>
> Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
> Reviewed-by: Oliver Upton <oupton@kernel.org>
> Link: https://patch.msgid.link/aiAZfdeyanIvP8SD@v4bel
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> [ Hyunwoo Kim: __kvm_at_s12() returns void in 6.12.y, so the context
>   differs from upstream (return; instead of return ret;). The
>   __kvm_find_s1_desc_level() hunk (Fixes: 50f77dc87f13) is dropped, as
>   that function is v6.18+ and absent here; only the __kvm_at_s12() /
>   kvm_walk_nested_s2() change (Fixes: be04cebf3e78) applies. ]
> Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>

I don't think this is necessary. 6.12 doesn't actually have NV support
(it was enabled only from userspace in 6.17), therefore the ATS12
emulation isn't reachable.

Thanks,

	M.

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