From patchwork Fri May 16 15:15:21 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Graf X-Patchwork-Id: 4193881 Return-Path: X-Original-To: patchwork-kvm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 8D5F09F387 for ; Fri, 16 May 2014 15:15:33 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id BDBF5202FF for ; Fri, 16 May 2014 15:15:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BFAE020270 for ; Fri, 16 May 2014 15:15:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757109AbaEPPP1 (ORCPT ); Fri, 16 May 2014 11:15:27 -0400 Received: from cantor2.suse.de ([195.135.220.15]:46736 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751789AbaEPPP0 (ORCPT ); Fri, 16 May 2014 11:15:26 -0400 Received: from relay2.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 6FBC6AD03; Fri, 16 May 2014 15:15:24 +0000 (UTC) From: Alexander Graf To: qemu-devel@nongnu.org Cc: kvm@vger.kernel.org, mtosatti@redhat.com, pbonzini@redhat.com Subject: [PATCH v2] kvmclock: Ensure time in migration never goes backward Date: Fri, 16 May 2014 17:15:21 +0200 Message-Id: <1400253321-9239-1-git-send-email-agraf@suse.de> X-Mailer: git-send-email 1.7.12.4 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Spam-Status: No, score=-7.5 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP When we migrate we ask the kernel about its current belief on what the guest time would be. However, I've seen cases where the kvmclock guest structure indicates a time more recent than the kvm returned time. To make sure we never go backwards, calculate what the guest would have seen as time at the point of migration and use that value instead of the kernel returned one when it's more recent. While the underlying bug is supposedly fixed on newer KVM versions, it doesn't hurt to base the view of the kvmclock after migration on the same foundation in host as well as guest. Signed-off-by: Alexander Graf Reviewed-by: Marcelo Tosatti --- v1 -> v2: - always use guest structure when available --- hw/i386/kvm/clock.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 48 insertions(+) diff --git a/hw/i386/kvm/clock.c b/hw/i386/kvm/clock.c index 892aa02..6f4ed28a 100644 --- a/hw/i386/kvm/clock.c +++ b/hw/i386/kvm/clock.c @@ -14,6 +14,7 @@ */ #include "qemu-common.h" +#include "qemu/host-utils.h" #include "sysemu/sysemu.h" #include "sysemu/kvm.h" #include "hw/sysbus.h" @@ -34,6 +35,47 @@ typedef struct KVMClockState { bool clock_valid; } KVMClockState; +struct pvclock_vcpu_time_info { + uint32_t version; + uint32_t pad0; + uint64_t tsc_timestamp; + uint64_t system_time; + uint32_t tsc_to_system_mul; + int8_t tsc_shift; + uint8_t flags; + uint8_t pad[2]; +} __attribute__((__packed__)); /* 32 bytes */ + +static uint64_t kvmclock_current_nsec(KVMClockState *s) +{ + CPUState *cpu = first_cpu; + CPUX86State *env = cpu->env_ptr; + hwaddr kvmclock_struct_pa = env->system_time_msr & ~1ULL; + uint64_t migration_tsc = env->tsc; + struct pvclock_vcpu_time_info time; + uint64_t delta; + uint64_t nsec_lo; + uint64_t nsec_hi; + uint64_t nsec; + + if (!(env->system_time_msr & 1ULL)) { + /* KVM clock not active */ + return 0; + } + + cpu_physical_memory_read(kvmclock_struct_pa, &time, sizeof(time)); + + delta = migration_tsc - time.tsc_timestamp; + if (time.tsc_shift < 0) { + delta >>= -time.tsc_shift; + } else { + delta <<= time.tsc_shift; + } + + mulu64(&nsec_lo, &nsec_hi, delta, time.tsc_to_system_mul); + nsec = (nsec_lo >> 32) | (nsec_hi << 32); + return nsec + time.system_time; +} static void kvmclock_vm_state_change(void *opaque, int running, RunState state) @@ -45,9 +87,15 @@ static void kvmclock_vm_state_change(void *opaque, int running, if (running) { struct kvm_clock_data data; + uint64_t time_at_migration = kvmclock_current_nsec(s); s->clock_valid = false; + /* We can't rely on the migrated clock value, just discard it */ + if (time_at_migration) { + s->clock = time_at_migration; + } + data.clock = s->clock; data.flags = 0; ret = kvm_vm_ioctl(kvm_state, KVM_SET_CLOCK, &data);