linux-kernel - Re: [REPOST PATCH 10/16] selftests: KVM: aarch64: Add KVM EVTYPE filter PMU test

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Date:   Tue, 7 Mar 2023 08:09:00 -0800
From:   Sean Christopherson <seanjc@...gle.com>
To:     Reiji Watanabe <reijiw@...gle.com>
Cc:     Raghavendra Rao Ananta <rananta@...gle.com>,
        Oliver Upton <oupton@...gle.com>,
        Marc Zyngier <maz@...nel.org>,
        Ricardo Koller <ricarkol@...gle.com>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jing Zhang <jingzhangos@...gle.com>,
        Colton Lewis <coltonlewis@...gle.com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [REPOST PATCH 10/16] selftests: KVM: aarch64: Add KVM EVTYPE
 filter PMU test

RESEND is the "standard" tag, not REPOST.

On Mon, Mar 06, 2023, Reiji Watanabe wrote:
> Hi Raghu,
> 
> On Tue, Feb 14, 2023 at 5:07 PM Raghavendra Rao Ananta
> <rananta@...gle.com> wrote:
> >
> > KVM doest't allow the guests to modify the filter types
> > such counting events in nonsecure/secure-EL2, EL3, and
> > so on. Validate the same by force-configuring the bits
> > in PMXEVTYPER_EL0, PMEVTYPERn_EL0, and PMCCFILTR_EL0
> > registers.
> >
> > The test extends further by trying to create an event
> > for counting only in EL2 and validates if the counter
> > is not progressing.
> >
> > Signed-off-by: Raghavendra Rao Ananta <rananta@...gle.com>
> > ---
> > +static void guest_evtype_filter_test(void)
> > +{
> > +       int i;
> > +       struct pmc_accessor *acc;
> > +       uint64_t typer, cnt;
> > +       struct arm_smccc_res res;
> > +
> > +       pmu_enable();
> > +
> > +       /*
> > +        * KVM blocks the guests from creating events for counting in Secure/Non-Secure Hyp (EL2),
> > +        * Monitor (EL3), and Multithreading configuration. It applies the mask
> > +        * ARMV8_PMU_EVTYPE_MASK against guest accesses to PMXEVTYPER_EL0, PMEVTYPERn_EL0,
> > +        * and PMCCFILTR_EL0 registers to prevent this. Check if KVM honors this using all possible
> > +        * ways to configure the EVTYPER.
> > +        */
> 
> I would prefer to break long lines into multiple lines for these comments
> (or other comments in these patches), as "Linux kernel coding style"
> suggests.

+1.  And on the other side of the coin, wrap the changelog closer to ~75 chars,
~54 chars is waaay too aggressive.