Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932118Ab0DOJoK (ORCPT ); Thu, 15 Apr 2010 05:44:10 -0400 Received: from 8bytes.org ([88.198.83.132]:54978 "EHLO 8bytes.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757666Ab0DOJoJ (ORCPT ); Thu, 15 Apr 2010 05:44:09 -0400 Date: Thu, 15 Apr 2010 11:44:07 +0200 From: oerg Roedel To: Avi Kivity Cc: "Zhang, Yanmin" , Ingo Molnar , Peter Zijlstra , Sheng Yang , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Marcelo Tosatti , 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 Message-ID: <20100415094407.GB12697@8bytes.org> References: <1902387910.2078.435.camel@ymzhang.sh.intel.com> <4BC588CF.5010507@redhat.com> <1902445479.2078.458.camel@ymzhang.sh.intel.com> <4BC6C8CD.1020801@redhat.com> <1902473858.2078.481.camel@ymzhang.sh.intel.com> <20100415090403.GA12697@8bytes.org> <4BC6D7C8.9060302@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4BC6D7C8.9060302@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: 1356 Lines: 40 On Thu, Apr 15, 2010 at 12:09:28PM +0300, Avi Kivity wrote: > On 04/15/2010 12:04 PM, oerg Roedel wrote: >> On Mon, Apr 15, 2030 at 04:57:38PM +0800, Zhang, Yanmin wrote: >> >> >>> I checked svm.c and it seems svm.c doesn't trigger a NMI to host if the NMI >>> happens in guest os. In addition, svm_complete_interrupts is called after >>> interrupt is enabled. >>> >> Yes. The NMI is held pending by the hardware until the STGI instruction >> is executed. >> And for nested svm the svm_complete_interrupts function needs to be >> executed after the nested exit handling. Therefore it is done late on >> svm. >> > > So, we'd need something like the following: > > if (exit == NMI) > __get_cpu_var(nmi_vcpu) = vcpu; > > stgi(); > > if (exit == NMI) { > while (!nmi_handled()) > cpu_relax(); > __get_cpu_var(nmi_vcpu) = NULL; > } Hmm, looks a bit complicated to me. The NMI should happen shortly after the stgi instruction. Interrupts are still disabled so we stay on this cpu. Can't we just set and erase the cpu_var at vcpu_load/vcpu_put time? Joerg -- 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/