From 95c9f56041b8d3b95644d790e2b3f59587805a01 Mon Sep 17 00:00:00 2001 From: David Gibson Date: Tue, 17 Sep 2019 03:47:09 +0200 Subject: [PATCH 3/4] migration: Do not re-read the clock on pre_save in case of paused guest RH-Author: David Gibson Message-id: <20190917034709.20167-1-dgibson@redhat.com> Patchwork-id: 90473 O-Subject: [RHEL-7.8 qemu-kvm-rhev PATCH] migration: Do not re-read the clock on pre_save in case of paused guest Bugzilla: 1743508 RH-Acked-by: Thomas Huth RH-Acked-by: Laurent Vivier RH-Acked-by: Dr. David Alan Gilbert 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=1743508 Brew: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=23524287 Testing: Booted a guest with the scratch qemu build Signed-off-by: David Gibson Signed-off-by: Miroslav Rezanina --- 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 ec4be25..fb90d19 100644 --- a/hw/ppc/ppc.c +++ b/hw/ppc/ppc.c @@ -877,6 +877,8 @@ 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) @@ -923,9 +925,9 @@ 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() * * @@ -940,7 +942,10 @@ 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 deaa46a..b900277 100644 --- a/target/ppc/cpu-qom.h +++ b/target/ppc/cpu-qom.h @@ -210,6 +210,7 @@ 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