linux-kernel - Re: [PATCH] KVM: PPC: Book3S HV: Fix guest time accounting with VIRT_CPU_ACCOUNTING

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Message-ID: <20180304224927.GB14569@fergus.ozlabs.ibm.com>
Date:   Mon, 5 Mar 2018 09:49:27 +1100
From:   Paul Mackerras <paulus@...abs.org>
To:     Laurent Vivier <lvivier@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        kvm-ppc@...r.kernel.org,
        David Gibson <david@...son.dropbear.id.au>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH] KVM: PPC: Book3S HV: Fix guest time accounting with
 VIRT_CPU_ACCOUNTING_GEN

On Fri, Mar 02, 2018 at 11:51:56AM +0100, Laurent Vivier wrote:
> Since commit 8b24e69fc47e ("KVM: PPC: Book3S HV: Close race with testing
> for signals on guest entry"), if CONFIG_VIRT_CPU_ACCOUNTING_GEN is set, the
> guest time is not accounted to guest time and user time, but instead to
> system time.
> 
> This is because guest_enter()/guest_exit() are called while interrupts
> are disabled and the tick counter cannot be updated between them.
> 
> To fix that, move guest_exit() after local_irq_enable(), and as
> guest_enter() is called with IRQ disabled, calls guest_enter_irqoff()
> instead.
> 
> Fixes: 8b24e69fc47e
> ("KVM: PPC: Book3S HV: Close race with testing for signals on guest entry")
> Signed-off-by: Laurent Vivier <lvivier@...hat.com>

Thanks, applied to my kvm-ppc-fixes branch.

Paul.