linux-kernel - Re: [PATCH v2 0/4] implement vcpu preempted check

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Date:	Thu, 7 Jul 2016 13:21:21 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Wanpeng Li <kernellwp@...il.com>
Cc:	Paolo Bonzini <pbonzini@...hat.com>,
	Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>,
	linux-s390 <linux-s390@...r.kernel.org>,
	Davidlohr Bueso <dave@...olabs.net>, mpe@...erman.id.au,
	boqun.feng@...il.com, will.deacon@....com,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Waiman Long <waiman.long@....com>,
	virtualization@...ts.linux-foundation.org,
	Ingo Molnar <mingo@...hat.com>,
	Paul Mackerras <paulus@...ba.org>, benh@...nel.crashing.org,
	schwidefsky@...ibm.com, Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	linuxppc-dev@...ts.ozlabs.org, kvm <kvm@...r.kernel.org>
Subject: Re: [PATCH v2 0/4] implement vcpu preempted check

On Thu, Jul 07, 2016 at 11:42:15AM +0200, Peter Zijlstra wrote:
> +static void update_steal_time_preempt(struct kvm_vcpu *vcpu)
> +{
> +	struct kvm_steal_time *st;
> +
> +	if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED))
> +		return;
> +
> +	if (unlikely(kvm_read_guest_cached(vcpu->kvm, &vcpu->arch.st.stime,
> +		&vcpu->arch.st.steal, sizeof(struct kvm_steal_time))))
> +		return;
> +
> +	st = &vcpu->arch.st.steal;
> +
> +	st->pad[KVM_ST_PAD_PREEMPT] = 1; /* we've stopped running */

So maybe have this be:

	... = kvm_vcpu_running();

That avoids marking the vcpu preempted when we do hlt and such.

> +	kvm_write_guest_cached(vcpu->kvm, &vcpu->arch.st.stime,
> +		st, sizeof(struct kvm_steal_time));
> +}