From patchwork Tue May 11 16:17:45 2010 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Glauber Costa X-Patchwork-Id: 98763 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by demeter.kernel.org (8.14.3/8.14.3) with ESMTP id o4BGOWs2002277 for ; Tue, 11 May 2010 16:24:33 GMT Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753969Ab0EKQW1 (ORCPT ); Tue, 11 May 2010 12:22:27 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41783 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753294Ab0EKQV3 (ORCPT ); Tue, 11 May 2010 12:21:29 -0400 Received: from int-mx04.intmail.prod.int.phx2.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.17]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id o4BGLSNj014704 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Tue, 11 May 2010 12:21:28 -0400 Received: from localhost.localdomain (virtlab1.virt.bos.redhat.com [10.16.72.21]) by int-mx04.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id o4BGLHQT003599; Tue, 11 May 2010 12:21:27 -0400 From: Glauber Costa To: kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org, avi@redhat.com, zamsden@redhat.com Subject: [PATCH 7/9] don't compute pvclock adjustments if we trust the tsc Date: Tue, 11 May 2010 12:17:45 -0400 Message-Id: <1273594667-17175-8-git-send-email-glommer@redhat.com> In-Reply-To: <1273594667-17175-7-git-send-email-glommer@redhat.com> References: <1273594667-17175-1-git-send-email-glommer@redhat.com> <1273594667-17175-2-git-send-email-glommer@redhat.com> <1273594667-17175-3-git-send-email-glommer@redhat.com> <1273594667-17175-4-git-send-email-glommer@redhat.com> <1273594667-17175-5-git-send-email-glommer@redhat.com> <1273594667-17175-6-git-send-email-glommer@redhat.com> <1273594667-17175-7-git-send-email-glommer@redhat.com> X-Scanned-By: MIMEDefang 2.67 on 10.5.11.17 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Greylist: IP, sender and recipient auto-whitelisted, not delayed by milter-greylist-4.2.3 (demeter.kernel.org [140.211.167.41]); Tue, 11 May 2010 16:24:33 +0000 (UTC) diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h index f019f8c..05eba5e 100644 --- a/arch/x86/include/asm/kvm_para.h +++ b/arch/x86/include/asm/kvm_para.h @@ -21,6 +21,11 @@ */ #define KVM_FEATURE_CLOCKSOURCE2 3 +/* The last 8 bits are used to indicate how to interpret the flags field + * in pvclock structure. If no bits are set, all flags are ignored. + */ +#define KVM_FEATURE_CLOCKSOURCE_STABLE_BIT 24 + #define MSR_KVM_WALL_CLOCK 0x11 #define MSR_KVM_SYSTEM_TIME 0x12 diff --git a/arch/x86/include/asm/pvclock-abi.h b/arch/x86/include/asm/pvclock-abi.h index ec5c41a..35f2d19 100644 --- a/arch/x86/include/asm/pvclock-abi.h +++ b/arch/x86/include/asm/pvclock-abi.h @@ -39,5 +39,6 @@ struct pvclock_wall_clock { u32 nsec; } __attribute__((__packed__)); +#define PVCLOCK_TSC_STABLE_BIT (1 << 0) #endif /* __ASSEMBLY__ */ #endif /* _ASM_X86_PVCLOCK_ABI_H */ diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c index 59c740f..eb9b76c 100644 --- a/arch/x86/kernel/kvmclock.c +++ b/arch/x86/kernel/kvmclock.c @@ -215,4 +215,7 @@ void __init kvmclock_init(void) clocksource_register(&kvm_clock); pv_info.paravirt_enabled = 1; pv_info.name = "KVM"; + + if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT)) + pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT); } diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c index f5bc40e..239427c 100644 --- a/arch/x86/kernel/pvclock.c +++ b/arch/x86/kernel/pvclock.c @@ -135,6 +135,10 @@ cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src) barrier(); } while (version != src->version); + if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) && + (shadow.flags & PVCLOCK_TSC_STABLE_BIT)) + return ret; + /* * Assumption here is that last_value, a global accumulator, always goes * forward. If we are less than that, we should not be much smaller.