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From 95c9f56041b8d3b95644d790e2b3f59587805a01 Mon Sep 17 00:00:00 2001
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From: David Gibson <dgibson@redhat.com>
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Date: Tue, 17 Sep 2019 03:47:09 +0200
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Subject: [PATCH 3/4] migration: Do not re-read the clock on pre_save in case
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of paused guest
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RH-Author: David Gibson <dgibson@redhat.com>
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Message-id: <20190917034709.20167-1-dgibson@redhat.com>
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Patchwork-id: 90473
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O-Subject: [RHEL-7.8 qemu-kvm-rhev PATCH] migration: Do not re-read the clock on pre_save in case of paused guest
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Bugzilla: 1743508
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RH-Acked-by: Thomas Huth <thuth@redhat.com>
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RH-Acked-by: Laurent Vivier <lvivier@redhat.com>
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RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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From: "Maxiwell S. Garcia" <maxiwell@linux.ibm.com>
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Re-read the timebase before migrate was ported from x86 commit:
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6053a86fe7bd: kvmclock: reduce kvmclock difference on migration
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The clock move makes the guest knows about the paused time between
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the stop and migrate commands. This is an issue in an already-paused
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VM because some side effects, like process stalls, could happen
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after migration.
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So, this patch checks the runstate of guest in the pre_save handler and
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do not re-reads the timebase in case of paused state (cold migration).
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Signed-off-by: Maxiwell S. Garcia <maxiwell@linux.ibm.com>
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Message-Id: <20190711194702.26598-1-maxiwell@linux.ibm.com>
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Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
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(cherry picked from commit d14f33976282a8744ca1bf1d64e73996c145aa3f)
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Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1743508
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Brew: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=23524287
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Testing: Booted a guest with the scratch qemu build
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Signed-off-by: David Gibson <dgibson@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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hw/ppc/ppc.c | 13 +++++++++----
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target/ppc/cpu-qom.h | 1 +
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2 files changed, 10 insertions(+), 4 deletions(-)
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diff --git a/hw/ppc/ppc.c b/hw/ppc/ppc.c
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index ec4be25..fb90d19 100644
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--- a/hw/ppc/ppc.c
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+++ b/hw/ppc/ppc.c
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@@ -877,6 +877,8 @@ static void timebase_save(PPCTimebase *tb)
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* there is no need to update it from KVM here
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*/
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tb->guest_timebase = ticks + first_ppc_cpu->env.tb_env->tb_offset;
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+
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+ tb->runstate_paused = runstate_check(RUN_STATE_PAUSED);
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}
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static void timebase_load(PPCTimebase *tb)
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@@ -923,9 +925,9 @@ void cpu_ppc_clock_vm_state_change(void *opaque, int running,
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}
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/*
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- * When migrating, read the clock just before migration,
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- * so that the guest clock counts during the events
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- * between:
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+ * When migrating a running guest, read the clock just
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+ * before migration, so that the guest clock counts
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+ * during the events between:
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*
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* * vm_stop()
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* *
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@@ -940,7 +942,10 @@ static int timebase_pre_save(void *opaque)
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{
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PPCTimebase *tb = opaque;
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- timebase_save(tb);
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+ /* guest_timebase won't be overridden in case of paused guest */
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+ if (!tb->runstate_paused) {
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+ timebase_save(tb);
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+ }
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return 0;
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}
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diff --git a/target/ppc/cpu-qom.h b/target/ppc/cpu-qom.h
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index deaa46a..b900277 100644
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--- a/target/ppc/cpu-qom.h
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+++ b/target/ppc/cpu-qom.h
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@@ -210,6 +210,7 @@ typedef struct PowerPCCPUClass {
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typedef struct PPCTimebase {
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uint64_t guest_timebase;
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int64_t time_of_the_day_ns;
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+ bool runstate_paused;
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} PPCTimebase;
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extern const struct VMStateDescription vmstate_ppc_timebase;
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--
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1.8.3.1
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