Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757960AbZDKTsq (ORCPT ); Sat, 11 Apr 2009 15:48:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755540AbZDKTsi (ORCPT ); Sat, 11 Apr 2009 15:48:38 -0400 Received: from relay3.ptmail.sapo.pt ([212.55.154.23]:56284 "HELO sapo.pt" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with SMTP id S1754741AbZDKTsh (ORCPT ); Sat, 11 Apr 2009 15:48:37 -0400 X-AntiVirus: PTMail-AV 0.3-0.92.0 Date: Sat, 11 Apr 2009 20:45:46 +0100 From: Luis Henriques To: Avi Kivity Cc: Ingo Molnar , Peter Zijlstra , linux-kernel@vger.kernel.org, Andrea Arcangeli Subject: Re: Problem with kvm on -tip Message-ID: <20090411194546.GA12126@hades.domain.com> References: <20090409210738.GA4566@hades.domain.com> <49E08857.2090503@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <49E08857.2090503@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1828 Lines: 53 Hi, On Sat, Apr 11, 2009 at 03:08:55PM +0300, Avi Kivity wrote: > > This might be fixed by the attached patch. I confirm that the patch you sent removes the warnings but does it really solve the issue? (Sorry, I really do not know this code so I might be saying something really stupid.) What I understand from your patch is that the only portion of code that needs protection is the __get_cpu_var(). If this is true then a patch like the one below would do a better job. But I am not sure that nothing else needs protection since the code immediately following the preempt_enable (in your patch) is an invocation to local_irq_save()... --- arch/x86/kvm/x86.c | 10 +++++++--- 1 files changed, 7 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 8ca100a..cf918b5 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -626,13 +626,17 @@ static void kvm_write_guest_time(struct kvm_vcpu *v) unsigned long flags; struct kvm_vcpu_arch *vcpu = &v->arch; void *shared_kaddr; + uint32_t tsc_khz; if ((!vcpu->time_page)) return; - if (unlikely(vcpu->hv_clock_tsc_khz != __get_cpu_var(cpu_tsc_khz))) { - kvm_set_time_scale(__get_cpu_var(cpu_tsc_khz), &vcpu->hv_clock); - vcpu->hv_clock_tsc_khz = __get_cpu_var(cpu_tsc_khz); + preempt_disable(); + tsc_khz = __get_cpu_var(cpu_tsc_khz); + preempt_enable(); + if (unlikely(vcpu->hv_clock_tsc_khz != tsc_khz)) { + kvm_set_time_scale(tsc_khz, &vcpu->hv_clock); + vcpu->hv_clock_tsc_khz = tsc_khz; } /* Keep irq disabled to prevent changes to the clock */ -- 1.6.2.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/