Re: [Qemu-devel] [PATCH v7 06/13] vfio: Add VM state change handler to know state of VM

[Yan Zhao]

On Fri, Jul 12, 2019 at 03:14:03AM +0800, Kirti Wankhede wrote:
> 
> 
> On 7/11/2019 5:43 PM, Dr. David Alan Gilbert wrote:
> > * Kirti Wankhede (address@hidden) wrote:
> >> VM state change handler gets called on change in VM's state. This is used 
> >> to set
> >> VFIO device state to _RUNNING.
> >> VM state change handler, migration state change handler and log_sync 
> >> listener
> >> are called asynchronously, which sometimes lead to data corruption in 
> >> migration
> >> region. Initialised mutex that is used to serialize operations on 
> >> migration data
> >> region during saving state.
> >>
> >> Signed-off-by: Kirti Wankhede <address@hidden>
> >> Reviewed-by: Neo Jia <address@hidden>
> >> ---
> >>  hw/vfio/migration.c           | 64 
> >> +++++++++++++++++++++++++++++++++++++++++++
> >>  hw/vfio/trace-events          |  2 ++
> >>  include/hw/vfio/vfio-common.h |  4 +++
> >>  3 files changed, 70 insertions(+)
> >>
> >> diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
> >> index a2cfbd5af2e1..c01f08b659d0 100644
> >> --- a/hw/vfio/migration.c
> >> +++ b/hw/vfio/migration.c
> >> @@ -78,6 +78,60 @@ err:
> >>      return ret;
> >>  }
> >>  
> >> +static int vfio_migration_set_state(VFIODevice *vbasedev, uint32_t state)
> >> +{
> >> +    VFIOMigration *migration = vbasedev->migration;
> >> +    VFIORegion *region = &migration->region.buffer;
> >> +    uint32_t device_state;
> >> +    int ret = 0;
> >> +
> >> +    device_state = (state & VFIO_DEVICE_STATE_MASK) |
> >> +                   (vbasedev->device_state & ~VFIO_DEVICE_STATE_MASK);
> >> +
> >> +    if ((device_state & VFIO_DEVICE_STATE_MASK) == 
> >> VFIO_DEVICE_STATE_INVALID) {
> >> +        return -EINVAL;
> >> +    }
> >> +
> >> +    ret = pwrite(vbasedev->fd, &device_state, sizeof(device_state),
> >> +                 region->fd_offset + offsetof(struct 
> >> vfio_device_migration_info,
> >> +                                              device_state));
> >> +    if (ret < 0) {
> >> +        error_report("%s: Failed to set device state %d %s",
> >> +                     vbasedev->name, ret, strerror(errno));
> >> +        return ret;
> >> +    }
> >> +
> >> +    vbasedev->device_state = device_state;
> >> +    trace_vfio_migration_set_state(vbasedev->name, device_state);
> >> +    return 0;
> >> +}
> >> +
> >> +static void vfio_vmstate_change(void *opaque, int running, RunState state)
> >> +{
> >> +    VFIODevice *vbasedev = opaque;
> >> +
> >> +    if ((vbasedev->vm_running != running)) {
> >> +        int ret;
> >> +        uint32_t dev_state;
> >> +
> >> +        if (running) {
> >> +            dev_state = VFIO_DEVICE_STATE_RUNNING;
> >> +        } else {
> >> +            dev_state = (vbasedev->device_state & VFIO_DEVICE_STATE_MASK) 
> >> &
> >> +                     ~VFIO_DEVICE_STATE_RUNNING;
> >> +        }
> >> +
> >> +        ret = vfio_migration_set_state(vbasedev, dev_state);
> >> +        if (ret) {
> >> +            error_report("%s: Failed to set device state 0x%x",
> >> +                         vbasedev->name, dev_state);
> >> +        }
> >> +        vbasedev->vm_running = running;
> >> +        trace_vfio_vmstate_change(vbasedev->name, running, 
> >> RunState_str(state),
> >> +                                  dev_state);
> >> +    }
> >> +}
> >> +
> >>  static int vfio_migration_init(VFIODevice *vbasedev,
> >>                                 struct vfio_region_info *info)
> >>  {
> >> @@ -93,6 +147,11 @@ static int vfio_migration_init(VFIODevice *vbasedev,
> >>          return ret;
> >>      }
> >>  
> >> +    qemu_mutex_init(&vbasedev->migration->lock);
> > 
> > Does this and it's friend below belong in this patch?  As far as I can
> > tell you init/deinit the lock here but don't use it which is strange.
> > 
> 
> This lock is used in
> 0009-vfio-Add-save-state-functions-to-SaveVMHandlers.patch and
> 0011-vfio-Add-function-to-get-dirty-page-list.patch
> 
> Hm. I'll move this init/deinit to patch 0009 in next iteration.
> 
> Thanks,
> Kirti
>
This lock is used to protect vfio_save_buffer and read dirty page,
right?
if data subregion and bitmap subregion do not reuse "data_offset" in
vfio_device_migration_info.
It seems that this lock can be avoided.

Thanks
Yan


> 
> > Dave
> > 
> >> +    vbasedev->vm_state = 
> >> qemu_add_vm_change_state_handler(vfio_vmstate_change,
> >> +                                                          vbasedev);
> >> +
> >>      return 0;
> >>  }
> >>  
> >> @@ -135,11 +194,16 @@ void vfio_migration_finalize(VFIODevice *vbasedev)
> >>          return;
> >>      }
> >>  
> >> +    if (vbasedev->vm_state) {
> >> +        qemu_del_vm_change_state_handler(vbasedev->vm_state);
> >> +    }
> >> +
> >>      if (vbasedev->migration_blocker) {
> >>          migrate_del_blocker(vbasedev->migration_blocker);
> >>          error_free(vbasedev->migration_blocker);
> >>      }
> >>  
> >> +    qemu_mutex_destroy(&vbasedev->migration->lock);
> >>      vfio_migration_region_exit(vbasedev);
> >>      g_free(vbasedev->migration);
> >>  }
> >> diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
> >> index 191a726a1312..3d15bacd031a 100644
> >> --- a/hw/vfio/trace-events
> >> +++ b/hw/vfio/trace-events
> >> @@ -146,3 +146,5 @@ vfio_display_edid_write_error(void) ""
> >>  
> >>  # migration.c
> >>  vfio_migration_probe(char *name, uint32_t index) " (%s) Region %d"
> >> +vfio_migration_set_state(char *name, uint32_t state) " (%s) state %d"
> >> +vfio_vmstate_change(char *name, int running, const char *reason, uint32_t 
> >> dev_state) " (%s) running %d reason %s device state %d"
> >> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> >> index 152da3f8d6f3..f6c70db3a9c1 100644
> >> --- a/include/hw/vfio/vfio-common.h
> >> +++ b/include/hw/vfio/vfio-common.h
> >> @@ -29,6 +29,7 @@
> >>  #ifdef CONFIG_LINUX
> >>  #include <linux/vfio.h>
> >>  #endif
> >> +#include "sysemu/sysemu.h"
> >>  
> >>  #define VFIO_MSG_PREFIX "vfio %s: "
> >>  
> >> @@ -124,6 +125,9 @@ typedef struct VFIODevice {
> >>      unsigned int flags;
> >>      VFIOMigration *migration;
> >>      Error *migration_blocker;
> >> +    uint32_t device_state;
> >> +    VMChangeStateEntry *vm_state;
> >> +    int vm_running;
> >>  } VFIODevice;
> >>  
> >>  struct VFIODeviceOps {
> >> -- 
> >> 2.7.0
> >>
> > --
> > Dr. David Alan Gilbert / address@hidden / Manchester, UK
> >