Re: [PATCH v2 26/28] KVM: arm64: Add FEAT_NV3 detection

[Marc Zyngier <maz@kernel.org>]

On Tue, 14 Jul 2026 11:07:03 +0100,
sashiko-bot@kernel.org wrote:
> 
> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> 
> Pre-existing issues:
> - [High] Writes to control-plane system registers (SYS_NVHCR_EL2 and SYS_VNCR_EL2) are missing the architecturally required `isb()` synchronization barrier.
> --
> 
> --- Patch [26]: [PATCH v2 26/28] KVM: arm64: Add FEAT_NV3 detection ---
> commit 1e08d22547f3313a77b075620f905436357c4b40
> Author: Marc Zyngier <maz@kernel.org>
> 
> KVM: arm64: Add FEAT_NV3 detection
>     
> Now that everything is in place to engage the FEAT_NV3 fast-path,
> add the detection code to cpufeature.c.
> 
> > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> > index c9c124b0ccc8e..6ae1c816e2010 100644
> > --- a/arch/arm64/kernel/cpufeature.c
> > +++ b/arch/arm64/kernel/cpufeature.c
> > @@ -2627,6 +2627,13 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
> >  		.matches = has_cpuid_feature,
> >  		ARM64_CPUID_FIELDS(ID_AA64MMFR4_EL1, NV_frac, NV2P1)
> >  	},
> > +	{
> > +		.desc = "FEAT_NV3",
> > +		.capability = ARM64_HAS_NV3,
> > +		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
> > +		.matches = has_cpuid_feature,
> > +		ARM64_CPUID_FIELDS(ID_AA64MMFR4_EL1, NV_frac, NV3)
> > +	},
> 
> [Severity: High]
> This isn't a bug introduced by this patch, but enabling FEAT_NV3 here exposes
> pre-existing paths where control-plane system registers are written without
> the architecturally required immediate isb() synchronization barrier.

Plonk.

	M.

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