From 8b0a69f11052d271ef49db0051d79e7f1a6102be Mon Sep 17 00:00:00 2001 From: David Gibson Date: Mon, 2 Sep 2019 04:20:32 +0100 Subject: [PATCH 1/6] migration: Do not re-read the clock on pre_save in case of paused guest MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit RH-Author: David Gibson Message-id: <20190902042032.25987-1-dgibson@redhat.com> Patchwork-id: 90226 O-Subject: [RHEL-AV-8.1.0 qemu-kvm PATCH] migration: Do not re-read the clock on pre_save in case of paused guest Bugzilla: 1747836 RH-Acked-by: Thomas Huth RH-Acked-by: Philippe Mathieu-Daudé RH-Acked-by: Laurent Vivier From: "Maxiwell S. Garcia" Re-read the timebase before migrate was ported from x86 commit: 6053a86fe7bd: kvmclock: reduce kvmclock difference on migration The clock move makes the guest knows about the paused time between the stop and migrate commands. This is an issue in an already-paused VM because some side effects, like process stalls, could happen after migration. So, this patch checks the runstate of guest in the pre_save handler and do not re-reads the timebase in case of paused state (cold migration). Signed-off-by: Maxiwell S. Garcia Message-Id: <20190711194702.26598-1-maxiwell@linux.ibm.com> Signed-off-by: David Gibson (cherry picked from commit d14f33976282a8744ca1bf1d64e73996c145aa3f) Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1747836 Branch: rhel8/rhel-av-8.1.0/master-4.1.0 Brew: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=23282250 Testing: Booted guest with this qemu Signed-off-by: David Gibson Signed-off-by: Danilo C. L. de Paula --- hw/ppc/ppc.c | 13 +++++++++---- target/ppc/cpu-qom.h | 1 + 2 files changed, 10 insertions(+), 4 deletions(-) diff --git a/hw/ppc/ppc.c b/hw/ppc/ppc.c index a9e508c..8572e45 100644 --- a/hw/ppc/ppc.c +++ b/hw/ppc/ppc.c @@ -1008,6 +1008,8 @@ static void timebase_save(PPCTimebase *tb) * there is no need to update it from KVM here */ tb->guest_timebase = ticks + first_ppc_cpu->env.tb_env->tb_offset; + + tb->runstate_paused = runstate_check(RUN_STATE_PAUSED); } static void timebase_load(PPCTimebase *tb) @@ -1051,9 +1053,9 @@ void cpu_ppc_clock_vm_state_change(void *opaque, int running, } /* - * When migrating, read the clock just before migration, - * so that the guest clock counts during the events - * between: + * When migrating a running guest, read the clock just + * before migration, so that the guest clock counts + * during the events between: * * * vm_stop() * * @@ -1068,7 +1070,10 @@ static int timebase_pre_save(void *opaque) { PPCTimebase *tb = opaque; - timebase_save(tb); + /* guest_timebase won't be overridden in case of paused guest */ + if (!tb->runstate_paused) { + timebase_save(tb); + } return 0; } diff --git a/target/ppc/cpu-qom.h b/target/ppc/cpu-qom.h index be9b4c3..5fbcdee 100644 --- a/target/ppc/cpu-qom.h +++ b/target/ppc/cpu-qom.h @@ -201,6 +201,7 @@ typedef struct PowerPCCPUClass { typedef struct PPCTimebase { uint64_t guest_timebase; int64_t time_of_the_day_ns; + bool runstate_paused; } PPCTimebase; extern const struct VMStateDescription vmstate_ppc_timebase; -- 1.8.3.1