Re: [Qemu-devel] [Question] virtio-serial misses irq delivery on migration?

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Gonglei (Arei) (arei.gonglei@huawei.com) wrote:
> Hi Dave,
> 
> 
> > -----Original Message-----
> > From: Dr. David Alan Gilbert [mailto:dgilbert@redhat.com]
> > Sent: Monday, August 08, 2016 8:13 PM
> > To: Gonglei (Arei)
> > Cc: Paolo Bonzini; jan.kiszka@siemens.com; amit.shah@redhat.com;
> > quintela@redhat.com; Huangweidong (C); qemu-devel@nongnu.org;
> > kvm@vger.kernel.org
> > Subject: Re: [Qemu-devel] [Question] virtio-serial misses irq delivery on
> > migration?
> > 
> > * Gonglei (Arei) (arei.gonglei@huawei.com) wrote:
> > > Hi all,
> > >
> > > I might catch the bug. Now, we rely on a vm_clock timer to assure that the
> > vcpus are started
> > > before we invoke send_control_event(),which queue a message in the virtio
> > ring and trigger a irq.
> > >
> > > In actually, we can't attach our initial intention under a special situation:
> > >
> > > 1. the process of migration destination is in a coroutine
> > >  Commit 82a4da79fd6
> > > 2. The corountine will yiled the cpu (calling yield_until_fd_readable(s->fd))
> > >  if the Qemu encounter a EAGIN while reading QEMUFile.
> > >  commit 595ab64169b
> > >
> > > static ssize_t socket_get_buffer(void *opaque, uint8_t *buf, int64_t pos,
> > >                                  size_t size)
> > > {
> > >     QEMUFileSocket *s = opaque;
> > >     ssize_t len;
> > >
> > >     for (;;) {
> > >         len = qemu_recv(s->fd, buf, size, 0);
> > >         if (len != -1) {
> > >             break;
> > >         }
> > >         if (socket_error() == EAGAIN) {
> > >             yield_until_fd_readable(s->fd);
> > >         } else if (socket_error() != EINTR) {
> > >             break;
> > >         }
> > >     }
> > >
> > >     if (len == -1) {
> > >         len = -socket_error();
> > >     }
> > >     return len;
> > > }
> > >
> > > 3. The main thread can get the cpu and timer will run, asumes that we get
> > EAGIN
> > >   after invoking fetch_active_ports_list().
> > 
> > I don't understand the details of this interrupt injection, or why the timer
> > will run if we're still not finished migration; it doesn't sound right that a
> > QEMU_CLOCK_VIRTUAL
> > timer should trigger while we're still receiving the VM and the guest is paused.
> > 
> 
> Because the migration coroutine will yiled cpu if it get a EAGAIN error from unix socket.
> You can see the above step 2)
> 
> For the upstream qemu, you can see the hander of QIO_CHANNEL_ERR_BLOCK in channel_get_buffer()
> 
> static ssize_t channel_get_buffer(void *opaque,
>                                   uint8_t *buf,
>                                   int64_t pos,
>                                   size_t size)
> {
>     QIOChannel *ioc = QIO_CHANNEL(opaque);
>     ssize_t ret;
> 
>     do {
>         ret = qio_channel_read(ioc, (char *)buf, size, NULL);
>         if (ret < 0) {
>             if (ret == QIO_CHANNEL_ERR_BLOCK) {
>                 qio_channel_yield(ioc, G_IO_IN);   // yiled cpu
>             } else {
>                 /* XXX handle Error * object */
>                 return -EIO;
>             }
>         }
>     } while (ret == QIO_CHANNEL_ERR_BLOCK);
> 
>     return ret;
> }

Yes, I understand it yields; but I would have expected the timer code
not to fire virtual timers while the VM is in paused state.

> > However, would it be fixed by using a vm_change_state_handler like
> > ui/spice-core.c does?
> > 
> 
> I'll check this method, thanks!
> 

Dave

> Regards,
> -Gonglei
> 
> > Dave
> > 
> > 
> > > 4. reproduce the problem by fault injection.
> > >
> > > The debug logs:
> > >
> > > [2016-08-06 16:52:56] handle_qmp_command:5106 qmp_cmd_name:
> > query-migrate-capabilities
> > > [2016-08-06 16:52:56] handle_qmp_command:5116 qmp_cmd_name:
> > migrate-set-capabilities, qmp_cmd_arguments: {"capabilities": [{"state": false,
> > "capability": "xbzrle"}]}
> > > [2016-08-06 16:52:56] handle_qmp_command:5106 qmp_cmd_name:
> > query-migrate-capabilities
> > > [2016-08-06 16:52:56] handle_qmp_command:5116 qmp_cmd_name:
> > migrate-set-capabilities, qmp_cmd_arguments: {"capabilities": [{"state": false,
> > "capability": "rdma-pin-all"}]}
> > > [2016-08-06 16:52:56] process_incoming_migration_co:170 gonglei: enter
> > process_incoming_migration_co()    // Enter corountine
> > > [2016-08-06 16:53:01] apic_dispatch_post_load:370 gonglei:
> > apic_dispatch_post_load
> > > [2016-08-06 16:53:01] apic_dispatch_post_load:370 gonglei:
> > apic_dispatch_post_load
> > > [2016-08-06 16:53:01] apic_dispatch_post_load:370 gonglei:
> > apic_dispatch_post_load
> > > [2016-08-06 16:53:01] apic_dispatch_post_load:370 gonglei:
> > apic_dispatch_post_load
> > > [2016-08-06 16:53:01] apic_dispatch_post_load:370 gonglei:
> > apic_dispatch_post_load
> > > [2016-08-06 16:53:01] apic_dispatch_post_load:370 gonglei:
> > apic_dispatch_post_load
> > > [2016-08-06 16:53:01] apic_dispatch_post_load:370 gonglei:
> > apic_dispatch_post_load
> > > [2016-08-06 16:53:01] apic_dispatch_post_load:370 gonglei:
> > apic_dispatch_post_load
> > > [2016-08-06 16:53:01] kvm_ioapic_put:97 gonglei: kvm_ioapic_put
> > > [2016-08-06 16:53:01] virtio_serial_load:745 gonglei: virtio_serial_load will
> > init virtqueue
> > > [2016-08-06 16:53:01] fetch_active_ports_list:735 gonglei: **************
> > begin to inject debug **********    // fault injection begin, migration
> > coroutine yiled cpu
> > > [2016-08-06 16:53:01] timerlist_run_timers:496 gonglei: expire_time: 1,
> > current_time: 9750771061592    //vm_clock timer boom
> > > [2016-08-06 16:53:01] virtio_serial_post_load_timer_cb:658 gonglei:
> > virtio_serial_post_load_timer_cb   //calling the timer callback
> > > [2016-08-06 16:53:01] send_control_event:225 virtio serial port 1 send
> > control message event = 6, value = 0 // send a message to the guest, raise the
> > irq line.
> > > [2016-08-06 16:53:01] virtio_serial_post_load_timer_cb:669 gonglei:
> > port->host_connected: 0
> > > [2016-08-06 16:53:01] monitor_qapi_event_emit:483 {"timestamp":
> > {"seconds": 1470473581, "microseconds": 64056}, "event":
> > "VSERPORT_CHANGE", "data": {"open": true, "id": "channel0"}}
> > > [2016-08-06 16:53:01] send_control_event:225 virtio serial port 3 send
> > control message event = 6, value = 0
> > > [2016-08-06 16:53:01] virtio_serial_post_load_timer_cb:669 gonglei:
> > port->host_connected: 0
> > > [2016-08-06 16:53:01] timerlist_run_timers:496 gonglei: expire_time:
> > 9750770788478, current_time: 9750771061592
> > > [2016-08-06 16:53:01] kvm_put_apic_state:32 gonglei: kvm_put_apic_state
> > //Enter migration coroutine again, and the restore the lapic register, the
> > previous lapic's info will be covered :(
> > > [2016-08-06 16:53:01] kvm_put_apic_state:32 gonglei: kvm_put_apic_state
> > > [2016-08-06 16:53:01] kvm_put_apic_state:32 gonglei: kvm_put_apic_state
> > > [2016-08-06 16:53:01] kvm_put_apic_state:32 gonglei: kvm_put_apic_state
> > > [2016-08-06 16:53:01] kvm_put_apic_state:32 gonglei: kvm_put_apic_state
> > > [2016-08-06 16:53:01] kvm_put_apic_state:32 gonglei: kvm_put_apic_state
> > > [2016-08-06 16:53:01] kvm_put_apic_state:32 gonglei: kvm_put_apic_state
> > > [2016-08-06 16:53:01] kvm_put_apic_state:32 gonglei: kvm_put_apic_state
> > > [2016-08-06 16:53:01] handle_qmp_command:5106 qmp_cmd_name: cont
> > > [2016-08-06 16:53:01] qmp_cont:189 qmp cont is received and vm is started
> > > [2016-08-06 16:53:01] vm_start:981 gonglei: enter vm_start
> > //enter vm_start here
> > > [2016-08-06 16:53:01] virtio_set_status:522 virtio-net device status is 7 that
> > means DRIVER OK
> > > [2016-08-06 16:53:01] virtio_set_status:522 virtio-serial device status is 7
> > that means DRIVER OK
> > > [2016-08-06 16:53:01] virtio_set_status:522 virtio-scsi device status is 7 that
> > means DRIVER OK
> > > [2016-08-06 16:53:01] vm_start:1000 vm_state-notify:23ms
> > > [2016-08-06 16:53:01] qemu_clock_enable:163 gonglei: type: 1, enabled: 1,
> > old: 1
> > > [2016-08-06 16:53:01] monitor_qapi_event_emit:483 {"timestamp":
> > {"seconds": 1470473581, "microseconds": 112191}, "event": "RESUME"}
> > > [2016-08-06 16:53:01] timerlist_run_timers:496 gonglei: expire_time:
> > 9750772061592, current_time: 9750794269805
> > > [2016-08-06 16:53:01] send_control_event:225 virtio serial port 1 send
> > control message event = 6, value = 1
> > > [2016-08-06 16:53:01] timerlist_run_timers:496 gonglei: expire_time:
> > 9750795284148, current_time: 9750795312685
> > > [2016-08-06 16:53:01] send_control_event:225 virtio serial port 3 send
> > control message event = 6, value = 1
> > > [2016-08-06 16:53:01] timerlist_run_timers:496 gonglei: expire_time:
> > 9750796329656, current_time: 9750796369458
> > > [2016-08-06 16:53:01] timerlist_run_timers:496 gonglei: expire_time:
> > 9750797396208, current_time: 9750797426752
> > > [2016-08-06 16:53:01] timerlist_run_timers:496 gonglei: expire_time:
> > 9750798445707, current_time: 9750798477520
> > > [2016-08-06 16:53:01] timerlist_run_timers:496 gonglei: expire_time:
> > 9750799496162, current_time: 9750799532183
> > > [2016-08-06 16:53:01] timerlist_run_timers:496 gonglei: expire_time:
> > 9750800556817, current_time: 9750800588741
> > > [2016-08-06 16:53:01] timerlist_run_timers:496 gonglei: expire_time:
> > 9750801606596, current_time: 9750801637961
> > >
> > >
> > > The below is my debugging diff (Not based on the newest master branch)
> > >
> > > diff --git a/hw/char/virtio-serial-bus.c b/hw/char/virtio-serial-bus.c
> > > index 6a45af9..a00b02f 100644
> > > --- a/hw/char/virtio-serial-bus.c
> > > +++ b/hw/char/virtio-serial-bus.c
> > > @@ -654,6 +654,7 @@ static void virtio_serial_post_load_timer_cb(void
> > *opaque)
> > >      if (!s->post_load) {
> > >          return;
> > >      }
> > > +    QEMU_LOG("gonglei: virtio_serial_post_load_timer_cb\n");
> > >      for (i = 0 ; i < s->post_load->nr_active_ports; ++i) {
> > >          port = s->post_load->connected[i].port;
> > >          host_connected = s->post_load->connected[i].host_connected;
> > > @@ -664,6 +665,7 @@ static void virtio_serial_post_load_timer_cb(void
> > *opaque)
> > >               */
> > >              send_control_event(s, port->id,
> > VIRTIO_CONSOLE_PORT_OPEN,
> > >                                 port->host_connected);
> > > +            QEMU_LOG("gonglei: port->host_connected: %u\n",
> > port->host_connected);
> > >          }
> > >          vsc = VIRTIO_SERIAL_PORT_GET_CLASS(port);
> > >          if (vsc->set_guest_connected) {
> > > @@ -729,6 +731,8 @@ static int fetch_active_ports_list(QEMUFile *f, int
> > version_id,
> > >          }
> > >      }
> > >      timer_mod(s->post_load->timer, 1);
> > > +    QEMU_LOG("gonglei: ************** begin to inject debug
> > **********\n");
> > > +    yield_until_fd_readable(qemu_get_fd(f));
> > >      return 0;
> > >  }
> > >
> > > @@ -737,7 +741,7 @@ static int virtio_serial_load(QEMUFile *f, void
> > *opaque, int version_id)
> > >      if (version_id > 3) {
> > >          return -EINVAL;
> > >      }
> > > -
> > > +    QEMU_LOG("gonglei: virtio_serial_load will init virtqueue\n");
> > >      /* The virtio device */
> > >      return virtio_load(VIRTIO_DEVICE(opaque), f, version_id);
> > >  }
> > > diff --git a/hw/i386/kvm/apic.c b/hw/i386/kvm/apic.c
> > > index 5b47056..2d988cb 100644
> > > --- a/hw/i386/kvm/apic.c
> > > +++ b/hw/i386/kvm/apic.c
> > > @@ -29,7 +29,7 @@ void kvm_put_apic_state(DeviceState *dev, struct
> > kvm_lapic_state *kapic)
> > >  {
> > >      APICCommonState *s = APIC_COMMON(dev);
> > >      int i;
> > > -
> > > +    QEMU_LOG("gonglei: kvm_put_apic_state\n");
> > >      memset(kapic, 0, sizeof(*kapic));
> > >      kvm_apic_set_reg(kapic, 0x2, s->id << 24);
> > >      kvm_apic_set_reg(kapic, 0x8, s->tpr);
> > > diff --git a/hw/i386/kvm/ioapic.c b/hw/i386/kvm/ioapic.c
> > > index d2a6c4c..07699ec 100644
> > > --- a/hw/i386/kvm/ioapic.c
> > > +++ b/hw/i386/kvm/ioapic.c
> > > @@ -94,7 +94,7 @@ static void kvm_ioapic_put(IOAPICCommonState *s)
> > >
> > >      chip.chip_id = KVM_IRQCHIP_IOAPIC;
> > >      kioapic = &chip.chip.ioapic;
> > > -
> > > +    QEMU_LOG("gonglei: kvm_ioapic_put\n");
> > >      kioapic->id = s->id;
> > >      kioapic->ioregsel = s->ioregsel;
> > >      kioapic->base_address = s->busdev.mmio[0].addr;
> > > diff --git a/hw/intc/apic_common.c b/hw/intc/apic_common.c
> > > index 042e960..110be20 100644
> > > --- a/hw/intc/apic_common.c
> > > +++ b/hw/intc/apic_common.c
> > > @@ -366,6 +366,7 @@ static int apic_dispatch_post_load(void *opaque, int
> > version_id)
> > >      if (info->post_load) {
> > >          info->post_load(s);
> > >      }
> > > +    QEMU_LOG("gonglei: apic_dispatch_post_load\n");
> > >      return 0;
> > >  }
> > >
> > > diff --git a/migration/migration.c b/migration/migration.c
> > > index 92c1427..d074c0a 100644
> > > --- a/migration/migration.c
> > > +++ b/migration/migration.c
> > > @@ -167,7 +167,7 @@ static void process_incoming_migration_co(void
> > *opaque)
> > >      const char *arpGuestCMD =
> > "{\"execute\":\"guest-write-flag-arp\"}\n";
> > >      const char *portName = "charchannel1";
> > >      size_t uRet;
> > > -
> > > +    QEMU_LOG("gonglei: enter process_incoming_migration_co()\n");
> > >      ret = qemu_loadvm_state(f);
> > >      qemu_fclose(f);
> > >      free_xbzrle_decoded_buf();
> > > diff --git a/qemu-timer.c b/qemu-timer.c
> > > index 5741f0d..dd36bc9 100644
> > > --- a/qemu-timer.c
> > > +++ b/qemu-timer.c
> > > @@ -160,6 +160,7 @@ void qemu_clock_enable(QEMUClockType type, bool
> > enabled)
> > >      QEMUTimerList *tl;
> > >      bool old = clock->enabled;
> > >      clock->enabled = enabled;
> > > +    QEMU_LOG("gonglei: type: %u, enabled: %u, old: %u\n", type, enabled,
> > old);
> > >      if (enabled && !old) {
> > >          qemu_clock_notify(type);
> > >      } else if (!enabled && old) {
> > > @@ -475,6 +476,7 @@ bool timerlist_run_timers(QEMUTimerList
> > *timer_list)
> > >      bool progress = false;
> > >      QEMUTimerCB *cb;
> > >      void *opaque;
> > > +    static int count = 10;
> > >
> > >      qemu_event_reset(&timer_list->timers_done_ev);
> > >      if (!timer_list->clock->enabled) {
> > > @@ -489,7 +491,10 @@ bool timerlist_run_timers(QEMUTimerList
> > *timer_list)
> > >              qemu_mutex_unlock(&timer_list->active_timers_lock);
> > >              break;
> > >          }
> > > -
> > > +	if (timer_list->clock->type == QEMU_CLOCK_VIRTUAL && count-- > 0) {
> > > +	    QEMU_LOG("gonglei: expire_time: %lld, current_time: %lld\n",
> > > +             ts->expire_time, current_time);
> > > +	}
> > >          /* remove timer from the list before calling the callback */
> > >          timer_list->active_timers = ts->next;
> > >          ts->next = NULL;
> > > diff --git a/vl.c b/vl.c
> > > index 06f34fe..824b246 100644
> > > --- a/vl.c
> > > +++ b/vl.c
> > > @@ -978,7 +978,7 @@ void vm_start(void)
> > >  {
> > >      RunState requested;
> > >      int64_t start_time, end_time;
> > > -
> > > +    QEMU_LOG("gonglei: enter vm_start\n");
> > >      qemu_vmstop_requested(&requested);
> > >      if (runstate_is_running() && requested == RUN_STATE_MAX) {
> > >          return;
> > >
> > >
> > > Can we wait looply the migration process finished when EAGAIN?
> > >
> > > Regards,
> > > -Gonglei
> > >
> > >
> > > > -----Original Message-----
> > > > From: Gonglei (Arei)
> > > > Sent: Friday, August 05, 2016 5:14 PM
> > > > To: Paolo Bonzini; 'jan.kiszka@siemens.com'; 'amit.shah@redhat.com'
> > > > Cc: qemu-devel@nongnu.org; kvm@vger.kernel.org; Huangweidong (C)
> > > > Subject: [Question] virtio-serial misses irq delivery on migration?
> > > >
> > > > Hi Paolo , Jan, Amit
> > > >
> > > > Recently we encountered a problem that the virtio-serial can't work after
> > > > Migration in RH5.5 VM. The bigger problem is, I can't reproduce it. :(
> > > >
> > > > It's phenomenon was much like BZ 867366, the usb-table mouse didn't work
> > > > because
> > > > the uhci and virtio-serial shard the irq line (using IOAPIC, not MSI). The new
> > > > interrupt
> > > > can't be injected to VM because the irq line bit had been set to 1, but the
> > > > frontend
> > > > driver never handle it or never know it.
> > > >
> > > >  Bug 867366 - virtio-serial misses irq delivery on migration
> > > > https://bugzilla.redhat.com/show_bug.cgi?id=867366
> > > >
> > > > But my qemu is the newest qemu, Both commit
> > 80dcfb8532"virtio-serial-bus:
> > > > post_load
> > > > send_event when vm is running" and commit bc6b815d9e " virtio-serial:
> > > > propagate
> > > > guest_connected to the port on post_load" are applied.
> > > >
> > > > I noticed that Paolo posted another problem maybe have a pertential
> > problem
> > > > about
> > > > apic in Comment 23. But this patch
> > > >  https://bugzilla.redhat.com/attachment.cgi?id=635535&action=diff
> > > > haven't merged into qemu master.
> > > >
> > > > Would you give me some clues please? Thanks!
> > > >
> > > > Regards,
> > > > -Gonglei
> > > >
> > >
> > >
> > --
> > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK