On Thu, 25 Mar 2021 09:37:15 +0000,
Shameerali Kolothum Thodi [off-list ref] wrote:

quoted

-----Original Message-----
From: Marc Zyngier [mailto:maz@kernel.org]
Sent: 25 March 2021 09:33
To: Shameerali Kolothum Thodi <redacted>
Cc: kvmarm@lists.cs.columbia.edu; kvm@vger.kernel.org;
linux-arm-kernel@lists.infradead.org; stable@vger.kernel.org;
pbonzini@redhat.com; Linuxarm [off-list ref]
Subject: Re: [PATCH for-stable-5.10 2/2] KVM: arm64: Workaround firmware
wrongly advertising GICv2-on-v3 compatibility

On 2021-03-25 09:14, Shameer Kolothum wrote:

quoted

From: Marc Zyngier <maz@kernel.org>

commit 9739f6ef053f104a997165701c6e15582c4307ee upstream.

It looks like we have broken firmware out there that wrongly
advertises a GICv2 compatibility interface, despite the CPUs not being
able to deal with it.

To work around this, check that the CPU initialising KVM is actually
able to switch to MMIO instead of system registers, and use that as a
precondition to enable GICv2 compatibility in KVM.

Note that the detection happens on a single CPU. If the firmware is
lying *and* that the CPUs are asymetric, all hope is lost anyway.

Cc: stable@vger.kernel.org #5.10
Reported-by: Shameerali Kolothum Thodi
[off-list ref]
Tested-by: Shameer Kolothum <redacted>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Message-Id: [off-list ref]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Shameer Kolothum <redacted>

Please hold on on that.

This patch causes a regression, and needs a fix that is currently queued for 5.12
[1]. Once this hits upstream, please add the fix to the series and post it as a
whole.

Ok. Yes, I noted that. But was thinking if this goes through first
and then we can have a stable tag for that one, we can manage
it.

The problem is we'd end-up with 5.10 being subtly broken for a while,
and I want to avoid this.

Specially given that not having this series only affects broken
platforms, while having an incomplete series breaks working systems
(which is be counter productive).

Anyway, will wait now.

Thanks for that,

	M.

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