[PATCH 7/8] KVM: arm64: Workaround firmware wrongly advertising GICv2-on-v3 compatibility

[Marc Zyngier]

On Mon, 15 Mar 2021 12:55:42 +0000,
Shameerali Kolothum Thodi <shameerali.kolothum.thodi at huawei.com> wrote:
> 
> 
> 
> > -----Original Message-----
> > From: Marc Zyngier [mailto:maz at kernel.org]
> > Sent: 05 March 2021 18:53
> > To: Paolo Bonzini <pbonzini at redhat.com>
> > Cc: Alexandru Elisei <alexandru.elisei at arm.com>; Andre Przywara
> > <andre.przywara at arm.com>; Andrew Scull <ascull at google.com>; Catalin
> > Marinas <catalin.marinas at arm.com>; Christoffer Dall
> > <christoffer.dall at arm.com>; Howard Zhang <Howard.Zhang at arm.com>; Jia
> > He <justin.he at arm.com>; Mark Rutland <mark.rutland at arm.com>; Quentin
> > Perret <qperret at google.com>; Shameerali Kolothum Thodi
> > <shameerali.kolothum.thodi at huawei.com>; Suzuki K Poulose
> > <suzuki.poulose at arm.com>; Will Deacon <will at kernel.org>; James Morse
> > <james.morse at arm.com>; Julien Thierry <julien.thierry.kdev at gmail.com>;
> > kernel-team at android.com; linux-arm-kernel at lists.infradead.org;
> > kvmarm at lists.cs.columbia.edu; kvm at vger.kernel.org
> > Subject: [PATCH 7/8] KVM: arm64: Workaround firmware wrongly advertising
> > GICv2-on-v3 compatibility
> > 
> > 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.
> > 
> > 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>
> 
> Is it possible to add stable tag for this? Looks like we do have
> systems out there and reports issues.

It is already merged. Which kernel versions do you need that for? In
any case, please submit the backports, and I'll review them.

Thanks,

	M.

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