Re: [PATCH v3 1/1] irqchip/gic-v4.1: Disable vSGI upon (GIC CPUIF < v4.1) detection

On Wed, Mar 17, 2021 at 02:04:36PM +0000, Marc Zyngier wrote:

Hi Lorenzo,

Wed, 17 Mar 2021 10:07:19 +0000,
Lorenzo Pieralisi [off-list ref] wrote:

quoted

GIC CPU interfaces versions predating GIC v4.1 were not built to
accommodate vINTID within the vSGI range; as reported in the GIC
specifications (8.2 "Changes to the CPU interface"), it is
CONSTRAINED UNPREDICTABLE to deliver a vSGI to a PE with
ID_AA64PFR0_EL1.GIC < b0011.

Check the GIC CPUIF version by reading the SYS_ID_AA64_PFR0_EL1.

Disable vSGIs if a CPUIF version < 4.1 is detected to prevent using
vSGIs on systems where they may misbehave.

Signed-off-by: Lorenzo Pieralisi <redacted>
Cc: Marc Zyngier <maz@kernel.org>

Does it need to go in as a fix? or can it just be pushed into 5.13?
Given that there is no such HW in the wild just yet, I'm inclined to
do the latter...

I agree with you; it is to make the driver/vgic robust against HW
misconfigurations (because that's what they are and I am not aware of
any _existing_ HW with such a misconfiguration - yet), 5.13 will
perfectly do.

Thanks a lot.

Lorenzo

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