Re: [PATCH v3 03/22] KVM: arm64: Define PMI{CNTR,FILTR}_EL0 as undef_access

[Colton Lewis]

Hi Marc. Thanks for the review.

Marc Zyngier <maz@xxxxxxxxxx> writes:

> On Thu, 26 Jun 2025 21:04:39 +0100,
> Colton Lewis <coltonlewis@xxxxxxxxxx> wrote:

> > Because KVM isn't fully prepared to support these yet even though the
> > host PMUv3 driver does, define them as undef_access for now.

> > Signed-off-by: Colton Lewis <coltonlewis@xxxxxxxxxx>
> > ---
> >   arch/arm64/kvm/sys_regs.c | 3 +++
> >   1 file changed, 3 insertions(+)

> > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> > index 76c2f0da821f..99fdbe174202 100644
> > --- a/arch/arm64/kvm/sys_regs.c
> > +++ b/arch/arm64/kvm/sys_regs.c
> > @@ -3092,6 +3092,9 @@ static const struct sys_reg_desc sys_reg_descs[] =  
> > {
> >   	{ SYS_DESC(SYS_SVCR), undef_access, reset_val, SVCR, 0, .visibility =  
> > sme_visibility  },
> >   	{ SYS_DESC(SYS_FPMR), undef_access, reset_val, FPMR, 0, .visibility =  
> > fp8_visibility },

> > +	{ SYS_DESC(SYS_PMICNTR_EL0), undef_access },

> $ jq -r --arg FEAT "FEAT_PMUv3_ICNTR" -f ./dumpfeat.jq Features.json
> (FEAT_PMUv3_ICNTR --> v8Ap8)
> (FEAT_PMUv3_ICNTR --> FEAT_PMUv3p9)
> ((FEAT_PMUv3_ICNTR && FEAT_AA64EL2) --> FEAT_FGT2)

> If you have FEAT_PMUv3_ICNTR, then you have FEAT_FGT2. If you have
> FEAT_FGT2, then we already trap and UNDEF PMICNTR_EL0 without any
> further handling since 4bc0fe0898406 ("KVM: arm64: Add sanitisation
> for FEAT_FGT2 registers").

> > +	{ SYS_DESC(SYS_PMICFILTR_EL0), undef_access },

> Same thing.
> > +
> >   	{ PMU_SYS_REG(PMCR_EL0), .access = access_pmcr, .reset = reset_pmcr,
> >   	  .reg = PMCR_EL0, .get_user = get_pmcr, .set_user = set_pmcr },
> >   	{ PMU_SYS_REG(PMCNTENSET_EL0),

> So none of this is actually required.

Thanks for the context. I'll take this patch out.