linux-kernel - Re: [PATCH] arm64/perf: Replace PMU version number '0' with ID_AA64DFR0_EL1_PMUVer

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Date:   Mon, 28 Nov 2022 08:28:43 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, will@...nel.org,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64/perf: Replace PMU version number '0' with ID_AA64DFR0_EL1_PMUVer_NI

On Mon, 28 Nov 2022 03:06:15 +0000,
Anshuman Khandual <anshuman.khandual@....com> wrote:
> 
> 
> 
> On 11/28/22 08:24, Anshuman Khandual wrote:
> > __armv8pmu_probe_pmu() returns if detected PMU is either not implemented or
> > implementation defined. Extracted ID_AA64DFR0_EL1_PMUVer value, when PMU is
> > not implemented is '0' which can be replaced with ID_AA64DFR0_EL1_PMUVer_NI
> > defined as '0b0000'.
> > 
> > Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
> > Cc: Mark Rutland <mark.rutland@....com>
> > Cc: Will Deacon <will@...nel.org>
> > Cc: Catalin Marinas <catalin.marinas@....com>
> > Cc: linux-perf-users@...r.kernel.org
> > Cc: linux-kernel@...r.kernel.org
> > Cc: linux-arm-kernel@...ts.infradead.org
> > Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> > ---
> > This applies on v6.1-rc6
> > 
> >  arch/arm64/kernel/perf_event.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
> > index 85a3aaefc0fb..b638f584b4dd 100644
> > --- a/arch/arm64/kernel/perf_event.c
> > +++ b/arch/arm64/kernel/perf_event.c
> > @@ -1188,7 +1188,8 @@ static void __armv8pmu_probe_pmu(void *info)
> >  	dfr0 = read_sysreg(id_aa64dfr0_el1);
> >  	pmuver = cpuid_feature_extract_unsigned_field(dfr0,
> >  			ID_AA64DFR0_EL1_PMUVer_SHIFT);
> > -	if (pmuver == ID_AA64DFR0_EL1_PMUVer_IMP_DEF || pmuver == 0)
> > +	if (pmuver == ID_AA64DFR0_EL1_PMUVer_IMP_DEF ||
> > +	    pmuver == ID_AA64DFR0_EL1_PMUVer_NI)
> >  		return;
> >  
> >  	cpu_pmu->pmuver = pmuver;
> > --
> 
> + Marc Zyngier <maz@...nel.org>
> 
> There are some KVM related pmuver not-implemented check as well, should they be
> replaced in this patch or rather in a separate patch ?
> 
> arch/arm64/kvm/pmu-emul.c:      if (pmu->pmuver == 0 || pmu->pmuver == ID_AA64DFR0_EL1_PMUVer_IMP_DEF)
> arch/arm64/kvm/pmu-emul.c:              if (pmu->pmuver == 0 ||
> arch/arm64/kvm/pmu-emul.c:                  pmu->pmuver == ID_AA64DFR0_EL1_PMUVer_IMP_DEF)

Separate patch please, as I have a large KVM PMU rework already
queued.

Thanks,

	M.

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