From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: [PATCH v12 for-xen-4.5 02/20] x86/VPMU: Manage VPMU_CONTEXT_SAVE flag in vpmu_save_force() Date: Fri, 26 Sep 2014 10:49:31 -0400 Message-ID: <20140926144931.GA14378@laptop.dumpdata.com> References: <1411673336-32736-1-git-send-email-boris.ostrovsky@oracle.com> <1411673336-32736-3-git-send-email-boris.ostrovsky@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <1411673336-32736-3-git-send-email-boris.ostrovsky@oracle.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Boris Ostrovsky Cc: kevin.tian@intel.com, keir@xen.org, jbeulich@suse.com, jun.nakajima@intel.com, andrew.cooper3@citrix.com, tim@xen.org, dietmar.hahn@ts.fujitsu.com, xen-devel@lists.xen.org, Aravind.Gopalakrishnan@amd.com, suravee.suthikulpanit@amd.com, dgdegra@tycho.nsa.gov List-Id: xen-devel@lists.xenproject.org On Thu, Sep 25, 2014 at 03:28:38PM -0400, Boris Ostrovsky wrote: > There is a possibility that we set VPMU_CONTEXT_SAVE on VPMU context in > vpmu_load() and never clear it (because vpmu_save_force() will see > VPMU_CONTEXT_LOADED bit clear, which is possible on AMD processors) > > The problem is that amd_vpmu_save() assumes that if VPMU_CONTEXT_SAVE is set > then (1) we need to save counters and (2) we don't need to "stop" control > registers since they must have been stopped earlier. The latter may cause all > sorts of problem (like counters still running in a wrong guest and hypervisor > sending to that guest unexpected PMU interrupts). > > Since setting this flag is currently always done prior to calling > vpmu_save_force() let's both set and clear it there. > > Signed-off-by: Boris Ostrovsky Reviewed-by: Konrad Rzeszutek Wilk > --- > xen/arch/x86/hvm/vpmu.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/xen/arch/x86/hvm/vpmu.c b/xen/arch/x86/hvm/vpmu.c > index 15d5b6f..451b346 100644 > --- a/xen/arch/x86/hvm/vpmu.c > +++ b/xen/arch/x86/hvm/vpmu.c > @@ -130,6 +130,8 @@ static void vpmu_save_force(void *arg) > if ( !vpmu_is_set(vpmu, VPMU_CONTEXT_LOADED) ) > return; > > + vpmu_set(vpmu, VPMU_CONTEXT_SAVE); > + > if ( vpmu->arch_vpmu_ops ) > (void)vpmu->arch_vpmu_ops->arch_vpmu_save(v); > > @@ -178,7 +180,6 @@ void vpmu_load(struct vcpu *v) > */ > if ( vpmu_is_set(vpmu, VPMU_CONTEXT_LOADED) ) > { > - vpmu_set(vpmu, VPMU_CONTEXT_SAVE); > on_selected_cpus(cpumask_of(vpmu->last_pcpu), > vpmu_save_force, (void *)v, 1); > vpmu_reset(vpmu, VPMU_CONTEXT_LOADED); > @@ -195,7 +196,6 @@ void vpmu_load(struct vcpu *v) > vpmu = vcpu_vpmu(prev); > > /* Someone ran here before us */ > - vpmu_set(vpmu, VPMU_CONTEXT_SAVE); > vpmu_save_force(prev); > vpmu_reset(vpmu, VPMU_CONTEXT_LOADED); > > -- > 1.8.1.4 > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xen.org > http://lists.xen.org/xen-devel