From patchwork Mon May 3 15:52:06 2010 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Glauber Costa X-Patchwork-Id: 96496 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 o43FsnpM002330 for ; Mon, 3 May 2010 15:54:52 GMT Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932886Ab0ECPyV (ORCPT ); Mon, 3 May 2010 11:54:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36969 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759570Ab0ECPxz (ORCPT ); Mon, 3 May 2010 11:53:55 -0400 Received: from int-mx03.intmail.prod.int.phx2.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.16]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id o43Frtv3017165 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Mon, 3 May 2010 11:53:55 -0400 Received: from localhost.localdomain (virtlab1.virt.bos.redhat.com [10.16.72.21]) by int-mx03.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id o43FrnZe027074; Mon, 3 May 2010 11:53:54 -0400 From: Glauber Costa To: kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org, avi@redhat.com, zamsden@redhat.com Subject: [PATCH v2 6/7] don't compute pvclock adjustments if we trust the tsc Date: Mon, 3 May 2010 11:52:06 -0400 Message-Id: <1272901927-829-7-git-send-email-glommer@redhat.com> In-Reply-To: <1272901927-829-6-git-send-email-glommer@redhat.com> References: <1272901927-829-1-git-send-email-glommer@redhat.com> <1272901927-829-2-git-send-email-glommer@redhat.com> <1272901927-829-3-git-send-email-glommer@redhat.com> <1272901927-829-4-git-send-email-glommer@redhat.com> <1272901927-829-5-git-send-email-glommer@redhat.com> <1272901927-829-6-git-send-email-glommer@redhat.com> X-Scanned-By: MIMEDefang 2.67 on 10.5.11.16 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]); Mon, 03 May 2010 15:54:52 +0000 (UTC) diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h index f019f8c..6f1b878 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_TSC 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..b123bd7 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_STABLE_TSC (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..518de01 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_TSC)) + pvclock_set_flags(PVCLOCK_STABLE_TSC); } diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c index 3dff5fa..0d4fe0c 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_STABLE_TSC) && + (shadow.flags & PVCLOCK_STABLE_TSC)) + 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.