Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752496Ab0HTIJ3 (ORCPT ); Fri, 20 Aug 2010 04:09:29 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56711 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752463Ab0HTIJX (ORCPT ); Fri, 20 Aug 2010 04:09:23 -0400 From: Zachary Amsden To: kvm@vger.kernel.org Cc: Zachary Amsden , Avi Kivity , Marcelo Tosatti , Glauber Costa , Thomas Gleixner , John Stultz , linux-kernel@vger.kernel.org Subject: [KVM timekeeping 33/35] Indicate reliable TSC in kvmclock Date: Thu, 19 Aug 2010 22:07:47 -1000 Message-Id: <1282291669-25709-34-git-send-email-zamsden@redhat.com> In-Reply-To: <1282291669-25709-1-git-send-email-zamsden@redhat.com> References: <1282291669-25709-1-git-send-email-zamsden@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1802 Lines: 52 When no platform bugs have been detected, no TSC warps have been detected, and the hardware guarantees to us TSC does not change rate or stop with P-state or C-state changes, we can consider it reliable. Signed-off-by: Zachary Amsden --- arch/x86/kvm/x86.c | 10 +++++++++- 1 files changed, 9 insertions(+), 1 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 86f182a..a7fa24e 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -55,6 +55,7 @@ #include #include #include +#include #define MAX_IO_MSRS 256 #define CR0_RESERVED_BITS \ @@ -900,6 +901,13 @@ static void kvm_get_time_scale(uint32_t scaled_khz, uint32_t base_khz, static DEFINE_PER_CPU(unsigned long, cpu_tsc_khz); unsigned long max_tsc_khz; +static inline int kvm_tsc_reliable(void) +{ + return (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) && + boot_cpu_has(X86_FEATURE_NONSTOP_TSC) && + !check_tsc_unstable()); +} + static inline u64 nsec_to_cycles(struct kvm *kvm, u64 nsec) { return pvclock_scale_delta(nsec, kvm->arch.virtual_tsc_mult, @@ -1151,7 +1159,7 @@ static int kvm_guest_time_update(struct kvm_vcpu *v) vcpu->hv_clock.tsc_timestamp = tsc_timestamp; vcpu->hv_clock.system_time = kernel_ns + v->kvm->arch.kvmclock_offset; vcpu->last_kernel_ns = kernel_ns; - vcpu->hv_clock.flags = 0; + vcpu->hv_clock.flags = kvm_tsc_reliable() ? PVCLOCK_TSC_STABLE_BIT : 0; /* * The interface expects us to write an even number signaling that the -- 1.7.1 -- 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/