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Subject: Re: [RFC 3/3] KVM: arm64: pmu: Enforce PMEVTYPER evtCount size
To:     Will Deacon <will@kernel.org>
Cc:     eric.auger.pro@gmail.com, maz@kernel.org,
        linux-kernel@vger.kernel.org, kvmarm@lists.cs.columbia.edu,
        james.morse@arm.com, andrew.murray@arm.com, suzuki.poulose@arm.com,
        drjones@redhat.com
References: <20191204204426.9628-1-eric.auger@redhat.com>
 <20191204204426.9628-4-eric.auger@redhat.com>
 <20191205090232.GC8606@willie-the-truck>
From:   Auger Eric <eric.auger@redhat.com>
Message-ID: <c1a876be-49ab-0b5f-8ddd-1a47bcf89300@redhat.com>
Date:   Thu, 5 Dec 2019 10:37:24 +0100
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Hi Will,

On 12/5/19 10:02 AM, Will Deacon wrote:
> 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)?

You're right. It is RES0 and not RAZ. My mistake. Please ignore this patch.

Thank you for the feedback.

Eric
> 
> Will
>