Re: [PATCH 6.12.y] KVM: arm64: Take the SRCU lock for page table walks in fault injection and AT emulation

[Hyunwoo Kim <imv4bel@gmail.com>]

On Tue, Jun 09, 2026 at 11:33:09AM +0100, Marc Zyngier wrote:
> 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.

Ah, I see. Thank you for the review.

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


Best regards,
Hyunwoo Kim