From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Ahern Subject: Re: [PATCH 7/9] KVM: Expose the architectural performance monitoring CPUID leaf Date: Tue, 01 Nov 2011 10:24:41 -0600 Message-ID: <4EB01D49.6010309@gmail.com> References: <1319993624-20247-1-git-send-email-gleb@redhat.com> <1319993624-20247-8-git-send-email-gleb@redhat.com> <4EB01507.1020607@gmail.com> <20111101161815.GB16539@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, avi@redhat.com, mtosatti@redhat.com, linux-kernel@redhat.com, mingo@elte.hu, a.p.zijlstra@chello.nl, acme@ghostprotocols.net To: Gleb Natapov Return-path: Received: from mail-gx0-f174.google.com ([209.85.161.174]:58703 "EHLO mail-gx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753738Ab1KAQYq (ORCPT ); Tue, 1 Nov 2011 12:24:46 -0400 Received: by ggnb1 with SMTP id b1so7201701ggn.19 for ; Tue, 01 Nov 2011 09:24:45 -0700 (PDT) In-Reply-To: <20111101161815.GB16539@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 11/01/2011 10:18 AM, Gleb Natapov wrote: > On Tue, Nov 01, 2011 at 09:49:27AM -0600, David Ahern wrote: >> On 10/30/2011 10:53 AM, Gleb Natapov wrote: >>> From: Avi Kivity >>> >>> Provide a CPUID leaf that describes the emulated PMU. >>> >>> Signed-off-by: Avi Kivity >>> Signed-off-by: Gleb Natapov >>> --- >>> arch/x86/kvm/x86.c | 23 ++++++++++++++++++++++- >>> 1 files changed, 22 insertions(+), 1 deletions(-) >>> >>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >>> index 5ea4cb8..56153a9 100644 >>> --- a/arch/x86/kvm/x86.c >>> +++ b/arch/x86/kvm/x86.c >>> @@ -2543,6 +2543,28 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function, >>> } >>> case 9: >>> break; >>> + case 0xa: { /* Architectural Performance Monitoring */ >>> + struct x86_pmu_capability cap; >>> + >>> + perf_get_x86_pmu_capability(&cap); >>> + >>> + /* >>> + * Only support guest architectural pmu on a host >>> + * with architectural pmu. >>> + */ >>> + if (!cap.version) >>> + memset(&cap, 0, sizeof(cap)); >>> + >>> + entry->eax = min(cap.version, 2) >>> + | (cap.num_counters_gp << 8) >>> + | (cap.bit_width_gp << 16) >>> + | (cap.events_mask_len << 24); >>> + entry->ebx = cap.events_mask; >>> + entry->ecx = 0; >>> + entry->edx = cap.num_counters_fixed >>> + | (cap.bit_width_fixed << 5); >>> + break; >>> + } >> >> If PERF_EVENTS is disabled in the host kernel will KVM return the right >> thing for the guest that might have PERF_EVENTS enabled? >> > With correct implementation of perf_get_x86_pmu_capability() it should. > PERF_EVENTS disable version should set cap.version to zero, so guest will > find that vcpu does not provide architectural PMU. Ok. I was also thinking about kvm-kmod where newer KVM source is compiled against older kernels - which at one point had PERF_EVENTS as a configurable parameter. In this case it is possible to have perf events disabled host side yet enabled guest side. David