On Thu, 25 Mar 2021 09:37:15 +0000, Shameerali Kolothum Thodi <shameerali.kolothum.thodi@xxxxxxxxxx> wrote: > > > > > -----Original Message----- > > From: Marc Zyngier [mailto:maz@xxxxxxxxxx] > > Sent: 25 March 2021 09:33 > > To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@xxxxxxxxxx> > > Cc: kvmarm@xxxxxxxxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx; > > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; stable@xxxxxxxxxxxxxxx; > > pbonzini@xxxxxxxxxx; Linuxarm <linuxarm@xxxxxxxxxx> > > 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: > > > From: Marc Zyngier <maz@xxxxxxxxxx> > > > > > > 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@xxxxxxxxxxxxxxx #5.10 > > > Reported-by: Shameerali Kolothum Thodi > > > <shameerali.kolothum.thodi@xxxxxxxxxx> > > > Tested-by: Shameer Kolothum <shameerali.kolothum.thodi@xxxxxxxxxx> > > > Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx> > > > Message-Id: <20210305185254.3730990-8-maz@xxxxxxxxxx> > > > Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> > > > Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@xxxxxxxxxx> > > > > 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.
