From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936282AbeCBLwc (ORCPT ); Fri, 2 Mar 2018 06:52:32 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:48344 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S934748AbeCBLw1 (ORCPT ); Fri, 2 Mar 2018 06:52:27 -0500 Subject: Re: [PATCH] KVM: PPC: Book3S HV: Fix guest time accounting with VIRT_CPU_ACCOUNTING_GEN To: Laurent Vivier , linux-kernel@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org, kvm-ppc@vger.kernel.org, Paul Mackerras , David Gibson References: <20180302105156.19506-1-lvivier@redhat.com> From: Paolo Bonzini Message-ID: Date: Fri, 2 Mar 2018 12:52:24 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180302105156.19506-1-lvivier@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/03/2018 11:51, 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 Reviewed-by: Paolo Bonzini > --- > arch/powerpc/kvm/book3s_hv.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c > index 89707354c2ef..8274c2807202 100644 > --- a/arch/powerpc/kvm/book3s_hv.c > +++ b/arch/powerpc/kvm/book3s_hv.c > @@ -2885,7 +2885,7 @@ static noinline void kvmppc_run_core(struct kvmppc_vcore *vc) > */ > trace_hardirqs_on(); > > - guest_enter(); > + guest_enter_irqoff(); > > srcu_idx = srcu_read_lock(&vc->kvm->srcu); > > @@ -2893,8 +2893,6 @@ static noinline void kvmppc_run_core(struct kvmppc_vcore *vc) > > srcu_read_unlock(&vc->kvm->srcu, srcu_idx); > > - guest_exit(); > - > trace_hardirqs_off(); > set_irq_happened(trap); > > @@ -2937,6 +2935,7 @@ static noinline void kvmppc_run_core(struct kvmppc_vcore *vc) > kvmppc_set_host_core(pcpu); > > local_irq_enable(); > + guest_exit(); > > /* Let secondaries go back to the offline loop */ > for (i = 0; i < controlled_threads; ++i) { >