ppc: fix larx migration, fix record-replay

[PATCH 5/7] target/ppc: Fix timebase reset with record-replay

Posted by Nicholas Piggin 2 years, 5 months ago

Timebase save uses a random number for a legacy vmstate field, which
makes rr snapshot loading unbalanced. The easiest way to deal with this
is just to skip the rng if record-replay is active.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 hw/ppc/ppc.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/hw/ppc/ppc.c b/hw/ppc/ppc.c
index 82e4408c5c..7b7db30f95 100644
--- a/hw/ppc/ppc.c
+++ b/hw/ppc/ppc.c
@@ -32,6 +32,7 @@
 #include "qemu/main-loop.h"
 #include "qemu/error-report.h"
 #include "sysemu/kvm.h"
+#include "sysemu/replay.h"
 #include "sysemu/runstate.h"
 #include "kvm_ppc.h"
 #include "migration/vmstate.h"
@@ -933,8 +934,14 @@ static void timebase_save(PPCTimebase *tb)
         return;
     }
 
-    /* not used anymore, we keep it for compatibility */
-    tb->time_of_the_day_ns = qemu_clock_get_ns(QEMU_CLOCK_HOST);
+    if (replay_mode == REPLAY_MODE_NONE) {
+        /* not used anymore, we keep it for compatibility */
+        tb->time_of_the_day_ns = qemu_clock_get_ns(QEMU_CLOCK_HOST);
+    } else {
+        /* simpler for record-replay to avoid this event, compat not needed */
+        tb->time_of_the_day_ns = 0;
+    }
+
     /*
      * tb_offset is only expected to be changed by QEMU so
      * there is no need to update it from KVM here
-- 
2.40.1

Re: [PATCH 5/7] target/ppc: Fix timebase reset with record-replay

Posted by Pavel Dovgalyuk 2 years, 5 months ago

Reviewed-by: Pavel Dovgalyuk <Pavel.Dovgalyuk@ispras.ru>

On 23.06.2023 15:57, Nicholas Piggin wrote:
> Timebase save uses a random number for a legacy vmstate field, which
> makes rr snapshot loading unbalanced. The easiest way to deal with this
> is just to skip the rng if record-replay is active.
> 
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---
>   hw/ppc/ppc.c | 11 +++++++++--
>   1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/ppc/ppc.c b/hw/ppc/ppc.c
> index 82e4408c5c..7b7db30f95 100644
> --- a/hw/ppc/ppc.c
> +++ b/hw/ppc/ppc.c
> @@ -32,6 +32,7 @@
>   #include "qemu/main-loop.h"
>   #include "qemu/error-report.h"
>   #include "sysemu/kvm.h"
> +#include "sysemu/replay.h"
>   #include "sysemu/runstate.h"
>   #include "kvm_ppc.h"
>   #include "migration/vmstate.h"
> @@ -933,8 +934,14 @@ static void timebase_save(PPCTimebase *tb)
>           return;
>       }
>   
> -    /* not used anymore, we keep it for compatibility */
> -    tb->time_of_the_day_ns = qemu_clock_get_ns(QEMU_CLOCK_HOST);
> +    if (replay_mode == REPLAY_MODE_NONE) {
> +        /* not used anymore, we keep it for compatibility */
> +        tb->time_of_the_day_ns = qemu_clock_get_ns(QEMU_CLOCK_HOST);
> +    } else {
> +        /* simpler for record-replay to avoid this event, compat not needed */
> +        tb->time_of_the_day_ns = 0;
> +    }
> +
>       /*
>        * tb_offset is only expected to be changed by QEMU so
>        * there is no need to update it from KVM here