linux-kernel - Re: [PATCH v7 10/10] arm64: Retrieve stolen time as paravirtualized guest

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Message-ID: <20191025155708.GB999@C02TF0J2HF1T.local>
Date:   Fri, 25 Oct 2019 16:57:08 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Steven Price <steven.price@....com>
Cc:     Marc Zyngier <maz@...nel.org>, Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        Mark Rutland <mark.rutland@....com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Radim Krčmář <rkrcmar@...hat.com>,
        Suzuki K Pouloze <suzuki.poulose@....com>,
        linux-doc@...r.kernel.org, Russell King <linux@...linux.org.uk>,
        James Morse <james.morse@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Julien Thierry <julien.thierry.kdev@...il.com>
Subject: Re: [PATCH v7 10/10] arm64: Retrieve stolen time as paravirtualized
 guest

On Mon, Oct 21, 2019 at 04:28:23PM +0100, Steven Price wrote:
> Enable paravirtualization features when running under a hypervisor
> supporting the PV_TIME_ST hypercall.
> 
> For each (v)CPU, we ask the hypervisor for the location of a shared
> page which the hypervisor will use to report stolen time to us. We set
> pv_time_ops to the stolen time function which simply reads the stolen
> value from the shared page for a VCPU. We guarantee single-copy
> atomicity using READ_ONCE which means we can also read the stolen
> time for another VCPU than the currently running one while it is
> potentially being updated by the hypervisor.
> 
> Signed-off-by: Steven Price <steven.price@....com>

Acked-by: Catalin Marinas <catalin.marinas@....com>