Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754673Ab0DOIGJ (ORCPT ); Thu, 15 Apr 2010 04:06:09 -0400 Received: from mx1.redhat.com ([209.132.183.28]:20572 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752362Ab0DOIGE (ORCPT ); Thu, 15 Apr 2010 04:06:04 -0400 Message-ID: <4BC6C8CD.1020801@redhat.com> Date: Thu, 15 Apr 2010 11:05:33 +0300 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100330 Fedora/3.0.4-1.fc12 Thunderbird/3.0.4 MIME-Version: 1.0 To: "Zhang, Yanmin" CC: Ingo Molnar , Peter Zijlstra , Sheng Yang , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Marcelo Tosatti , oerg Roedel , Jes Sorensen , Gleb Natapov , Zachary Amsden , zhiteng.huang@intel.com, tim.c.chen@intel.com, Arnaldo Carvalho de Melo Subject: Re: [PATCH V3] perf & kvm: Enhance perf to collect KVM guest os statistics from host side References: <1902387910.2078.435.camel@ymzhang.sh.intel.com> <4BC588CF.5010507@redhat.com> <1902445479.2078.458.camel@ymzhang.sh.intel.com> In-Reply-To: <1902445479.2078.458.camel@ymzhang.sh.intel.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1794 Lines: 50 On 04/15/2030 04:04 AM, Zhang, Yanmin wrote: > >> An even more accurate way to determine this is to check whether the >> interrupt frame points back at the 'int $2' instruction. However we >> plan to switch to a self-IPI method to inject the NMI, and I'm not sure >> wether APIC NMIs are accepted on an instruction boundary or whether >> there's some latency involved. >> > Yes. But the frame pointer checking seems a little complicated. > An even bigger disadvantage is that it won't work with Sheng's patch, self-NMIs are not synchronous. >>> trace_kvm_entry(vcpu->vcpu_id); >>> + >>> + percpu_write(current_vcpu, vcpu); >>> kvm_x86_ops->run(vcpu); >>> + percpu_write(current_vcpu, NULL); >>> >>> >> If you move this around the 'int $2' instructions you will close the >> race, as a stray NMI won't catch us updating the rip cache. But that >> depends on whether self-IPI is accepted on the next instruction or not. >> > Right. The kernel part has dependency on the self-IPI implementation. > I will move above percpu_write(current_vcpu, vcpu) (or a new wrapper function) > just around 'int $2'. > > Or create a new function to inject the interrupt in x86.c. That will reduce duplication between svm.c and vmx.c. > Sheng would find a solution on the self-IPI delivery. Let's separate my patch > and self-IPI as 2 issues as we don't know when the self-IPI delivery would be > resolved. > Sure. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain. -- 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/