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Subject: Re: [PATCH v3 3/7] arm64/kvm: disable access to AMU registers from
 kvm guests
To:     Ionela Voinescu <ionela.voinescu@arm.com>, catalin.marinas@arm.com,
        will@kernel.org, mark.rutland@arm.com, maz@kernel.org,
        suzuki.poulose@arm.com, sudeep.holla@arm.com, lukasz.luba@arm.com,
        rjw@rjwysocki.net
Cc:     peterz@infradead.org, mingo@redhat.com, vincent.guittot@linaro.org,
        viresh.kumar@linaro.org, linux-arm-kernel@lists.infradead.org,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-pm@vger.kernel.org, James Morse <james.morse@arm.com>,
        Julien Thierry <julien.thierry.kdev@gmail.com>
References: <20200211184542.29585-1-ionela.voinescu@arm.com>
 <20200211184542.29585-4-ionela.voinescu@arm.com>
From:   Valentin Schneider <valentin.schneider@arm.com>
Message-ID: <a4d66284-a0fc-4bbb-3a98-ea4093bcf389@arm.com>
Date:   Wed, 12 Feb 2020 15:36:23 +0000
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On 11/02/2020 18:45, Ionela Voinescu wrote:
> Access to the AMU counters should be disabled by default in kvm guests,
> as information from the counters might reveal activity in other guests
> or activity on the host.
> 
> Therefore, disable access to AMU registers from EL0 and EL1 in kvm
> guests by:
>  - Hiding the presence of the extension in the feature register
>    (SYS_ID_AA64PFR0_EL1) on the VCPU.
>  - Disabling access to the AMU registers before switching to the guest.
>  - Trapping accesses and injecting an undefined instruction into the
>    guest.
> 
> Signed-off-by: Ionela Voinescu <ionela.voinescu@arm.com>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: James Morse <james.morse@arm.com>
> Cc: Julien Thierry <julien.thierry.kdev@gmail.com>
> Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>

Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>