Re: [Qemu-devel] latest rc: virtio-blk hangs forever after migration

[Marcelo Tosatti <mtosatti@redhat.com>]

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On Wed, Jul 16, 2014 at 12:38:51PM +0400, Andrey Korolyov wrote:
> On Wed, Jul 16, 2014 at 5:16 AM, Marcelo Tosatti <mtosatti@redhat.com> wrote:
> > On Wed, Jul 16, 2014 at 03:40:47AM +0400, Andrey Korolyov wrote:
> >> On Wed, Jul 16, 2014 at 2:01 AM, Paolo Bonzini <pbonzini@redhat.com> wrote:
> >> > Il 15/07/2014 23:25, Andrey Korolyov ha scritto:
> >> >
> >> >> On Wed, Jul 16, 2014 at 1:09 AM, Marcelo Tosatti <mtosatti@redhat.com>
> >> >> wrote:
> >> >>>
> >> >>> On Tue, Jul 15, 2014 at 06:01:08PM +0400, Andrey Korolyov wrote:
> >> >>>>
> >> >>>> On Tue, Jul 15, 2014 at 10:52 AM, Andrey Korolyov <andrey@xdel.ru>
> >> >>>> wrote:
> >> >>>>>
> >> >>>>> On Tue, Jul 15, 2014 at 9:03 AM, Amit Shah <amit.shah@redhat.com>
> >> >>>>> wrote:
> >> >>>>>>
> >> >>>>>> On (Sun) 13 Jul 2014 [16:28:56], Andrey Korolyov wrote:
> >> >>>>>>>
> >> >>>>>>> Hello,
> >> >>>>>>>
> >> >>>>>>> the issue is not specific to the iothread code because generic
> >> >>>>>>> virtio-blk also hangs up:
> >> >>>>>>
> >> >>>>>>
> >> >>>>>> Do you know which version works well?  If you could bisect, that'll
> >> >>>>>> help a lot.
> >> >>>>>>
> >> >>>>>> Thanks,
> >> >>>>>>                 Amit
> >> >>>>>
> >> >>>>>
> >> >>>>> Hi,
> >> >>>>>
> >> >>>>> 2.0 works definitely well. I`ll try to finish bisection today, though
> >> >>>>> every step takes about 10 minutes to complete.
> >> >>>>
> >> >>>>
> >> >>>> Yay! It is even outside of virtio-blk.
> >> >>>>
> >> >>>> commit 9b1786829aefb83f37a8f3135e3ea91c56001b56
> >> >>>> Author: Marcelo Tosatti <mtosatti@redhat.com>
> >> >>>> Date:   Tue Jun 3 13:34:48 2014 -0300
> >> >>>>
> >> >>>>     kvmclock: Ensure proper env->tsc value for kvmclock_current_nsec
> >> >>>> calculation
> >> >>>>
> >> >>>>     Ensure proper env->tsc value for kvmclock_current_nsec calculation.
> >> >>>>
> >> >>>>     Reported-by: Marcin Gibuła <m.gibula@beyond.pl>
> >> >>>>     Cc: qemu-stable@nongnu.org
> >> >>>>     Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> >> >>>>     Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> >> >>>
> >> >>>
> >> >>> Andrey,
> >> >>>
> >> >>> Can you please provide instructions on how to create reproducible
> >> >>> environment?
> >> >>>
> >> >>> The following patch is equivalent to the original patch, for
> >> >>> the purposes of fixing the kvmclock problem.
> >> >>>
> >> >>> Perhaps it becomes easier to spot the reason for the hang you are
> >> >>> experiencing.
> >> >>>
> >> >>>
> >> >>> diff --git a/hw/i386/kvm/clock.c b/hw/i386/kvm/clock.c
> >> >>> index 272a88a..feb5fc5 100644
> >> >>> --- a/hw/i386/kvm/clock.c
> >> >>> +++ b/hw/i386/kvm/clock.c
> >> >>> @@ -17,7 +17,6 @@
> >> >>>  #include "qemu/host-utils.h"
> >> >>>  #include "sysemu/sysemu.h"
> >> >>>  #include "sysemu/kvm.h"
> >> >>> -#include "sysemu/cpus.h"
> >> >>>  #include "hw/sysbus.h"
> >> >>>  #include "hw/kvm/clock.h"
> >> >>>
> >> >>> @@ -66,7 +65,6 @@ static uint64_t kvmclock_current_nsec(KVMClockState *s)
> >> >>>
> >> >>>      cpu_physical_memory_read(kvmclock_struct_pa, &time, sizeof(time));
> >> >>>
> >> >>> -    assert(time.tsc_timestamp <= migration_tsc);
> >> >>>      delta = migration_tsc - time.tsc_timestamp;
> >> >>>      if (time.tsc_shift < 0) {
> >> >>>          delta >>= -time.tsc_shift;
> >> >>> @@ -125,8 +123,6 @@ static void kvmclock_vm_state_change(void *opaque,
> >> >>> int running,
> >> >>>          if (s->clock_valid) {
> >> >>>              return;
> >> >>>          }
> >> >>> -
> >> >>> -        cpu_synchronize_all_states();
> >> >>>          ret = kvm_vm_ioctl(kvm_state, KVM_GET_CLOCK, &data);
> >> >>>          if (ret < 0) {
> >> >>>              fprintf(stderr, "KVM_GET_CLOCK failed: %s\n",
> >> >>> strerror(ret));
> >> >>> diff --git a/migration.c b/migration.c
> >> >>> index 8d675b3..34f2325 100644
> >> >>> --- a/migration.c
> >> >>> +++ b/migration.c
> >> >>> @@ -608,6 +608,7 @@ static void *migration_thread(void *opaque)
> >> >>>                  qemu_system_wakeup_request(QEMU_WAKEUP_REASON_OTHER);
> >> >>>                  old_vm_running = runstate_is_running();
> >> >>>
> >> >>> +                cpu_synchronize_all_states();
> >> >>>                  ret = vm_stop_force_state(RUN_STATE_FINISH_MIGRATE);
> >> >>>                  if (ret >= 0) {
> >> >>>                      qemu_file_set_rate_limit(s->file, INT64_MAX);
> >> >
> >> >
> >> > It could also be useful to apply the above patch _and_ revert
> >> > a096b3a6732f846ec57dc28b47ee9435aa0609bf, then try to reproduce.
> >> >
> >> > Paolo
> >>
> >> Yes, it solved the issue for me! (it took much time to check because
> >> most of country` debian mirrors went inconsistent by some reason)
> >>
> >> Also trivial addition:
> >>
> >> diff --git a/migration.c b/migration.c
> >> index 34f2325..65d1c88 100644
> >> --- a/migration.c
> >> +++ b/migration.c
> >> @@ -25,6 +25,7 @@
> >>  #include "qemu/thread.h"
> >>  #include "qmp-commands.h"
> >>  #include "trace.h"
> >> +#include "sysemu/cpus.h"
> >
> > And what about not reverting a096b3a6732f846ec57dc28b47ee9435aa0609bf ?
> >
> > That is, test with a stock qemu.git tree and the patch sent today,
> > on this thread, to move cpu_synchronize_all_states ?
> >
> >
> 
> The main reason for things to work for me is a revert of
> 9b1786829aefb83f37a8f3135e3ea91c56001b56 on top, not adding any other
> patches. I had tested two cases, with Alexander`s patch completely
> reverted plus suggestion from Marcelo and only with revert 9b178682
> plug same suggestion. The difference is that the until Alexander`
> patch is not reverted, live migration is always failing by the timeout
> value, and when reverted migration always succeeds in 8-10 seconds.
> Appropriate diffs are attached for the reference.

Andrey,

Can you please apply only the following attached patch to an upstream
QEMU git tree (move_synchronize_all_states.patch), plus the necessary
header file corrections, and attempt to reproduce?

When you reproduce, please provide a backtrace and version of the QEMU
git tree, and instructions on how to reproduce:

1) full QEMU command line
2) steps to reproduce
 


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Move cpu_synchronize_all_states to migration.c.

diff --git a/hw/i386/kvm/clock.c b/hw/i386/kvm/clock.c
index 272a88a..feb5fc5 100644
--- a/hw/i386/kvm/clock.c
+++ b/hw/i386/kvm/clock.c
@@ -17,7 +17,6 @@
 #include "qemu/host-utils.h"
 #include "sysemu/sysemu.h"
 #include "sysemu/kvm.h"
-#include "sysemu/cpus.h"
 #include "hw/sysbus.h"
 #include "hw/kvm/clock.h"
 
@@ -66,7 +65,6 @@ static uint64_t kvmclock_current_nsec(KVMClockState *s)
 
     cpu_physical_memory_read(kvmclock_struct_pa, &time, sizeof(time));
 
-    assert(time.tsc_timestamp <= migration_tsc);
     delta = migration_tsc - time.tsc_timestamp;
     if (time.tsc_shift < 0) {
         delta >>= -time.tsc_shift;
@@ -125,8 +123,6 @@ static void kvmclock_vm_state_change(void *opaque, int running,
         if (s->clock_valid) {
             return;
         }
-
-        cpu_synchronize_all_states();
         ret = kvm_vm_ioctl(kvm_state, KVM_GET_CLOCK, &data);
         if (ret < 0) {
             fprintf(stderr, "KVM_GET_CLOCK failed: %s\n", strerror(ret));
diff --git a/migration.c b/migration.c
index 8d675b3..34f2325 100644
--- a/migration.c
+++ b/migration.c
@@ -608,6 +608,7 @@ static void *migration_thread(void *opaque)
                 qemu_system_wakeup_request(QEMU_WAKEUP_REASON_OTHER);
                 old_vm_running = runstate_is_running();
 
+                cpu_synchronize_all_states();
                 ret = vm_stop_force_state(RUN_STATE_FINISH_MIGRATE);
                 if (ret >= 0) {
                     qemu_file_set_rate_limit(s->file, INT64_MAX);