linux-kernel - Re: [PATCH] KVM: PPC: Book3S HV: Remove vcpu->arch.dec usage

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Message-ID: <20180111100148.GJ24294@fergus.ozlabs.ibm.com>
Date:   Thu, 11 Jan 2018 21:01:48 +1100
From:   Paul Mackerras <paulus@...abs.org>
To:     Alexander Graf <agraf@...e.de>
Cc:     kvm-ppc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH] KVM: PPC: Book3S HV: Remove vcpu->arch.dec usage

On Tue, Dec 19, 2017 at 03:56:24PM +0100, Alexander Graf wrote:
> On Book3S in HV mode, we don't use the vcpu->arch.dec field at all.
> Instead, all logic is built around vcpu->arch.dec_expires.
> 
> So let's remove the one remaining piece of code that was setting it.
> 
> Signed-off-by: Alexander Graf <agraf@...e.de>

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

> Looking through the DEC logic, I fail to see any code that allows
> save or restore of DEC. Do we maybe miss out on that register for
> (live) migration?

Yes, it looks like we do.  I'm amazed no-one has noticed before.  I'll
fix it.

Paul.