[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Qemu-devel] [PATCH v2] migration: Do not re-read the clock on pre_save
From: |
Maxiwell S. Garcia |
Subject: |
[Qemu-devel] [PATCH v2] migration: Do not re-read the clock on pre_save in case of paused guest |
Date: |
Thu, 11 Jul 2019 16:47:02 -0300 |
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 <address@hidden>
---
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 a9e508c496..8572e45274 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 be9b4c30c3..5fbcdee9c9 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;
--
2.20.1
- [Qemu-devel] [PATCH v2] migration: Do not re-read the clock on pre_save in case of paused guest,
Maxiwell S. Garcia <=