linux-kernel - Re: [RFC 3/3] KVM: arm64: pmu: Enforce PMEVTYPER evtCount size

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Message-ID: <20191205090232.GC8606@willie-the-truck>
Date:   Thu, 5 Dec 2019 09:02:32 +0000
From:   Will Deacon <will@...nel.org>
To:     Eric Auger <eric.auger@...hat.com>
Cc:     eric.auger.pro@...il.com, maz@...nel.org,
        linux-kernel@...r.kernel.org, kvmarm@...ts.cs.columbia.edu,
        james.morse@....com, andrew.murray@....com, suzuki.poulose@....com,
        drjones@...hat.com
Subject: Re: [RFC 3/3] KVM: arm64: pmu: Enforce PMEVTYPER evtCount size

On Wed, Dec 04, 2019 at 09:44:26PM +0100, Eric Auger wrote:
> ARMv8.1-PMU supports 16-bit evtCount whereas 8.0 only supports
> 10 bits.
> 
> On Seatlle which has an 8.0 PMU implementation, evtCount[15:10]
> are not read as 0, as expected. Fix that by applying a mask on
> the selected event that depends on the PMU version.

Are you sure about that? These bits are RES0 in 8.0 afaict, so this would be
a CPU erratum. Have you checked the SDEN document (I haven't)?

Will