From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: [PATCH] KVM guest: prevent tracing recursion with kvmclock Date: Tue, 15 Nov 2011 15:12:16 +0200 Message-ID: <20111115131216.GG3225@redhat.com> References: <1321362075-27115-1-git-send-email-avi@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: kvm@vger.kernel.org, Steven Rostedt To: Avi Kivity Return-path: Received: from mx1.redhat.com ([209.132.183.28]:36530 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754512Ab1KONMU (ORCPT ); Tue, 15 Nov 2011 08:12:20 -0500 Content-Disposition: inline In-Reply-To: <1321362075-27115-1-git-send-email-avi@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Tue, Nov 15, 2011 at 03:01:15PM +0200, Avi Kivity wrote: > Stop tracing when we read the clock, since tracing will also > want to read the clock, and recurse indefinitely. > > Based on a similar patch for Xen from Jeremy Fitzhardinge. > > Signed-off-by: Avi Kivity Tested-by: Gleb Natapov > --- > arch/x86/kernel/kvmclock.c | 5 +++-- > 1 files changed, 3 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c > index c1a0188..44842d7 100644 > --- a/arch/x86/kernel/kvmclock.c > +++ b/arch/x86/kernel/kvmclock.c > @@ -74,9 +74,10 @@ static cycle_t kvm_clock_read(void) > struct pvclock_vcpu_time_info *src; > cycle_t ret; > > - src = &get_cpu_var(hv_clock); > + preempt_disable_notrace(); > + src = &__get_cpu_var(hv_clock); > ret = pvclock_clocksource_read(src); > - put_cpu_var(hv_clock); > + preempt_enable_notrace(); > return ret; > } > > -- > 1.7.7.1 -- Gleb.