[PATCH for-stable-5.10 2/2] KVM: arm64: Workaround firmware wrongly advertising GICv2-on-v3 compatibility

[Marc Zyngier]

On 2021-03-25 09:14, Shameer Kolothum wrote:
> From: Marc Zyngier <maz at 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 at vger.kernel.org #5.10
> Reported-by: Shameerali Kolothum Thodi 
> <shameerali.kolothum.thodi at huawei.com>
> Tested-by: Shameer Kolothum <shameerali.kolothum.thodi at huawei.com>
> Signed-off-by: Marc Zyngier <maz at kernel.org>
> Message-Id: <20210305185254.3730990-8-maz at kernel.org>
> Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
> Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi at huawei.com>

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.

Thanks,

         M.

[1] https://lore.kernel.org/r/20210323162301.2049595-1-maz@kernel.org
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