From: Will Deacon <will@kernel.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Shaokun Zhang <zhangshaokun@hisilicon.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 1/3] arm64: perf: Add support caps in sysfs
Date: Mon, 20 Jul 2020 11:54:10 +0100 [thread overview]
Message-ID: <20200720105410.GD11516@willie-the-truck> (raw)
In-Reply-To: <20200720105019.GA54220@C02TD0UTHF1T.local>
On Mon, Jul 20, 2020 at 11:50:19AM +0100, Mark Rutland wrote:
> On Mon, Jul 20, 2020 at 11:15:19AM +0100, Will Deacon wrote:
> > On Thu, Jun 18, 2020 at 09:35:42PM +0800, Shaokun Zhang wrote:
>
> > > +static umode_t
> > > +armv8pmu_caps_attr_is_visible(struct kobject *kobj, struct attribute *attr,
> > > + int unused)
> > > +{
> > > + int pmuver = armv8pmu_get_pmu_version();
> > > +
> > > + if (pmuver >= ID_AA64DFR0_PMUVER_8_4)
> > > + return attr->mode;
> >
> > Is this sufficient? I'm a bit confused by the text in the Arm ARM that says:
> >
> > | If ARMv8.4-PMU is implemented:
> > | * If STALL_SLOT is not implemented, it is IMPLEMENTATION DEFINED whether
> > | the PMMIR System registers are implemented.
> > | * If STALL_SLOT is implemented, then the PMMIR System registers are
> > | implemented.
> >
> > whereas the register description for PMMIR_EL1 says:
> >
> > | This register is present only when ARMv8.4-PMU is implemented.
>
> I think this is trying to say that when ARMv8.4-PMU is not implemented,
> PMMIR definitely isn't implemented (i.e. the the presence of PMMIR_EL1
> implies the presence of ARMv8.4-PMU).
>
> > Mark -- please could you clarify whether or not we need to check STALL_SLOT
> > as well as the PMUVer?
>
> Given the explciit wording that it's IMP DEF, I suspect that we need to
> check both.
>
> I'll go chase this up.
Thanks. In the meantime, Shaokun, can you send updated versions of the first
two patches, please? We'll play it safe and check STALL_SLOT as well pending
Mark's findings.
Will
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next prev parent reply other threads:[~2020-07-20 10:55 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-18 13:35 [PATCH v3 1/3] arm64: perf: Add support caps in sysfs Shaokun Zhang
2020-06-18 13:35 ` [PATCH v3 2/3] arm64: perf: Expose some new events via sysfs Shaokun Zhang
2020-07-20 10:16 ` Will Deacon
2020-06-18 13:35 ` [PATCH v3 3/3] arm64: perf: Correct the event index in sysfs Shaokun Zhang
2020-07-20 10:20 ` Will Deacon
2020-07-07 13:33 ` [PATCH v3 1/3] arm64: perf: Add support caps " Shaokun Zhang
2020-07-20 10:15 ` Will Deacon
2020-07-20 10:50 ` Mark Rutland
2020-07-20 10:54 ` Will Deacon [this message]
2020-07-20 13:11 ` Shaokun Zhang
2020-07-21 8:05 ` Shaokun Zhang
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