From patchwork Tue Jul 13 02:25:23 2010 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Zachary Amsden X-Patchwork-Id: 111647 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by demeter.kernel.org (8.14.4/8.14.3) with ESMTP id o6D2TuJp015637 for ; Tue, 13 Jul 2010 02:29:57 GMT Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756342Ab0GMCZw (ORCPT ); Mon, 12 Jul 2010 22:25:52 -0400 Received: from mx1.redhat.com ([209.132.183.28]:5938 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756421Ab0GMCZu (ORCPT ); Mon, 12 Jul 2010 22:25:50 -0400 Received: from int-mx05.intmail.prod.int.phx2.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.18]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id o6D2PoUu002323 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Mon, 12 Jul 2010 22:25:50 -0400 Received: from mysore (vpn-10-168.rdu.redhat.com [10.11.10.168]) by int-mx05.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id o6D2PfiY026035; Mon, 12 Jul 2010 22:25:48 -0400 From: Zachary Amsden To: KVM , Avi Kivity , Marcelo Tosatti , Glauber Costa Cc: Linux-kernel , Zachary Amsden , Avi Kivity , Marcelo Tosatti , Glauber Costa Subject: [PATCH 03/18] TSC reset compensation Date: Mon, 12 Jul 2010 16:25:23 -1000 Message-Id: <1278987938-23873-4-git-send-email-zamsden@redhat.com> In-Reply-To: <1278987938-23873-1-git-send-email-zamsden@redhat.com> References: <1278987938-23873-1-git-send-email-zamsden@redhat.com> X-Scanned-By: MIMEDefang 2.67 on 10.5.11.18 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, 13 Jul 2010 02:29:57 +0000 (UTC) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 3b4efe2..4b42893 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -396,6 +396,9 @@ struct kvm_arch { unsigned long irq_sources_bitmap; s64 kvmclock_offset; spinlock_t tsc_write_lock; + u64 last_tsc_nsec; + u64 last_tsc_offset; + u64 last_tsc_write; struct kvm_xen_hvm_config xen_hvm_config; diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index a2ee975..bb7451b 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -896,10 +896,39 @@ static DEFINE_PER_CPU(unsigned long, cpu_tsc_khz); void guest_write_tsc(struct kvm_vcpu *vcpu, u64 data) { struct kvm *kvm = vcpu->kvm; - u64 offset; + u64 offset, ns, elapsed; + struct timespec ts; spin_lock(&kvm->arch.tsc_write_lock); offset = data - native_read_tsc(); + ktime_get_ts(&ts); + monotonic_to_bootbased(&ts); + ns = timespec_to_ns(&ts); + elapsed = ns - kvm->arch.last_tsc_nsec; + + /* + * Special case: identical write to TSC within 5 seconds of + * another CPU is interpreted as an attempt to synchronize + * (the 5 seconds is to accomodate host load / swapping). + * + * In that case, for a reliable TSC, we can match TSC offsets, + * or make a best guest using kernel_ns value. + */ + if (data == kvm->arch.last_tsc_write && elapsed < 5ULL * NSEC_PER_SEC) { + if (!check_tsc_unstable()) { + offset = kvm->arch.last_tsc_offset; + pr_debug("kvm: matched tsc offset for %llu\n", data); + } else { + u64 tsc_delta = elapsed * __get_cpu_var(cpu_tsc_khz); + tsc_delta = tsc_delta / USEC_PER_SEC; + offset += tsc_delta; + pr_debug("kvm: adjusted tsc offset by %llu\n", tsc_delta); + } + ns = kvm->arch.last_tsc_nsec; + } + kvm->arch.last_tsc_nsec = ns; + kvm->arch.last_tsc_write = data; + kvm->arch.last_tsc_offset = offset; kvm_x86_ops->write_tsc_offset(vcpu, offset); spin_unlock(&kvm->arch.tsc_write_lock);