Re: [PATCH QEMU v25 09/17] vfio: Add load state functions to SaveVMHandlers

[Alex Williamson <alex.williamson@redhat.com>]

On Thu, 25 Jun 2020 19:46:22 +0530
Kirti Wankhede <kwankhede@nvidia.com> wrote:

> On 6/25/2020 12:24 AM, Alex Williamson wrote:
> > On Sun, 21 Jun 2020 01:51:18 +0530
> > Kirti Wankhede <kwankhede@nvidia.com> wrote:
> >   
> >> Sequence  during _RESUMING device state:
> >> While data for this device is available, repeat below steps:
> >> a. read data_offset from where user application should write data.
> >> b. write data of data_size to migration region from data_offset.
> >> c. write data_size which indicates vendor driver that data is written in
> >>     staging buffer.
> >>
> >> For user, data is opaque. User should write data in the same order as
> >> received.
> >>
> >> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
> >> Reviewed-by: Neo Jia <cjia@nvidia.com>
> >> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> >> ---
> >>   hw/vfio/migration.c  | 177 +++++++++++++++++++++++++++++++++++++++++++++++++++
> >>   hw/vfio/trace-events |   3 +
> >>   2 files changed, 180 insertions(+)
> >>
> >> diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
> >> index ef1150c1ff02..faacea5327cb 100644
> >> --- a/hw/vfio/migration.c
> >> +++ b/hw/vfio/migration.c
> >> @@ -302,6 +302,33 @@ static int vfio_save_device_config_state(QEMUFile *f, void *opaque)
> >>       return qemu_file_get_error(f);
> >>   }
> >>   
> >> +static int vfio_load_device_config_state(QEMUFile *f, void *opaque)
> >> +{
> >> +    VFIODevice *vbasedev = opaque;
> >> +    uint64_t data;
> >> +
> >> +    if (vbasedev->ops && vbasedev->ops->vfio_load_config) {
> >> +        int ret;
> >> +
> >> +        ret = vbasedev->ops->vfio_load_config(vbasedev, f);
> >> +        if (ret) {
> >> +            error_report("%s: Failed to load device config space",
> >> +                         vbasedev->name);
> >> +            return ret;
> >> +        }
> >> +    }
> >> +
> >> +    data = qemu_get_be64(f);
> >> +    if (data != VFIO_MIG_FLAG_END_OF_STATE) {
> >> +        error_report("%s: Failed loading device config space, "
> >> +                     "end flag incorrect 0x%"PRIx64, vbasedev->name, data);
> >> +        return -EINVAL;
> >> +    }
> >> +
> >> +    trace_vfio_load_device_config_state(vbasedev->name);
> >> +    return qemu_file_get_error(f);
> >> +}
> >> +
> >>   /* ---------------------------------------------------------------------- */
> >>   
> >>   static int vfio_save_setup(QEMUFile *f, void *opaque)
> >> @@ -472,12 +499,162 @@ static int vfio_save_complete_precopy(QEMUFile *f, void *opaque)
> >>       return ret;
> >>   }
> >>   
> >> +static int vfio_load_setup(QEMUFile *f, void *opaque)
> >> +{
> >> +    VFIODevice *vbasedev = opaque;
> >> +    VFIOMigration *migration = vbasedev->migration;
> >> +    int ret = 0;
> >> +
> >> +    if (migration->region.mmaps) {
> >> +        ret = vfio_region_mmap(&migration->region);
> >> +        if (ret) {
> >> +            error_report("%s: Failed to mmap VFIO migration region %d: %s",
> >> +                         vbasedev->name, migration->region.nr,
> >> +                         strerror(-ret));
> >> +            return ret;  
> > 
> > 
> > Not fatal.
> >  
> 
> As discussed on 07/17 patch of this series, it should fall back to 
> read/write, right?

Yes, it's worth an error_report() but not a migration abort imo.
Thanks,

Alex

> >> +        }
> >> +    }
> >> +
> >> +    ret = vfio_migration_set_state(vbasedev, ~VFIO_DEVICE_STATE_MASK,
> >> +                                   VFIO_DEVICE_STATE_RESUMING);
> >> +    if (ret) {
> >> +        error_report("%s: Failed to set state RESUMING", vbasedev->name);
> >> +    }
> >> +    return ret;
> >> +}
> >> +
> >> +static int vfio_load_cleanup(void *opaque)
> >> +{
> >> +    vfio_save_cleanup(opaque);
> >> +    return 0;
> >> +}
> >> +
> >> +static int vfio_load_state(QEMUFile *f, void *opaque, int version_id)
> >> +{
> >> +    VFIODevice *vbasedev = opaque;
> >> +    VFIOMigration *migration = vbasedev->migration;
> >> +    int ret = 0;
> >> +    uint64_t data, data_size;
> >> +
> >> +    data = qemu_get_be64(f);
> >> +    while (data != VFIO_MIG_FLAG_END_OF_STATE) {
> >> +
> >> +        trace_vfio_load_state(vbasedev->name, data);
> >> +
> >> +        switch (data) {
> >> +        case VFIO_MIG_FLAG_DEV_CONFIG_STATE:
> >> +        {
> >> +            ret = vfio_load_device_config_state(f, opaque);
> >> +            if (ret) {
> >> +                return ret;
> >> +            }
> >> +            break;
> >> +        }
> >> +        case VFIO_MIG_FLAG_DEV_SETUP_STATE:
> >> +        {
> >> +            data = qemu_get_be64(f);
> >> +            if (data == VFIO_MIG_FLAG_END_OF_STATE) {
> >> +                return ret;
> >> +            } else {
> >> +                error_report("%s: SETUP STATE: EOS not found 0x%"PRIx64,
> >> +                             vbasedev->name, data);
> >> +                return -EINVAL;  
> > 
> > This is essentially just a compatibility failure, right?  For instance
> > some future version of QEMU might include additional data between these
> > markers that we don't understand and therefore we fail the migration.
> >   
> 
> Yes.
> 
> Thanks,
> Kirti
> 
> Thanks,
> > 
> > Alex
> >   
> >> +            }
> >> +            break;
> >> +        }
> >> +        case VFIO_MIG_FLAG_DEV_DATA_STATE:
> >> +        {
> >> +            VFIORegion *region = &migration->region;
> >> +            uint64_t data_offset = 0, size;
> >> +
> >> +            data_size = size = qemu_get_be64(f);
> >> +            if (data_size == 0) {
> >> +                break;
> >> +            }
> >> +
> >> +            ret = pread(vbasedev->fd, &data_offset, sizeof(data_offset),
> >> +                        region->fd_offset +
> >> +                        offsetof(struct vfio_device_migration_info,
> >> +                        data_offset));
> >> +            if (ret != sizeof(data_offset)) {
> >> +                error_report("%s:Failed to get migration buffer data offset %d",
> >> +                             vbasedev->name, ret);
> >> +                return -EINVAL;
> >> +            }
> >> +
> >> +            trace_vfio_load_state_device_data(vbasedev->name, data_offset,
> >> +                                              data_size);
> >> +
> >> +            while (size) {
> >> +                void *buf = NULL;
> >> +                uint64_t sec_size;
> >> +                bool buffer_mmaped;
> >> +
> >> +                buf = get_data_section_size(region, data_offset, size,
> >> +                                            &sec_size);
> >> +
> >> +                buffer_mmaped = (buf != NULL);
> >> +
> >> +                if (!buffer_mmaped) {
> >> +                    buf = g_try_malloc(sec_size);
> >> +                    if (!buf) {
> >> +                        error_report("%s: Error allocating buffer ", __func__);
> >> +                        return -ENOMEM;
> >> +                    }
> >> +                }
> >> +
> >> +                qemu_get_buffer(f, buf, sec_size);
> >> +
> >> +                if (!buffer_mmaped) {
> >> +                    ret = pwrite(vbasedev->fd, buf, sec_size,
> >> +                                 region->fd_offset + data_offset);
> >> +                    g_free(buf);
> >> +
> >> +                    if (ret != sec_size) {
> >> +                        error_report("%s: Failed to set migration buffer %d",
> >> +                                vbasedev->name, ret);
> >> +                        return -EINVAL;
> >> +                    }
> >> +                }
> >> +                size -= sec_size;
> >> +                data_offset += sec_size;
> >> +            }
> >> +
> >> +            ret = pwrite(vbasedev->fd, &data_size, sizeof(data_size),
> >> +                         region->fd_offset +
> >> +                       offsetof(struct vfio_device_migration_info, data_size));
> >> +            if (ret != sizeof(data_size)) {
> >> +                error_report("%s: Failed to set migration buffer data size %d",
> >> +                             vbasedev->name, ret);
> >> +                return -EINVAL;
> >> +            }
> >> +            break;
> >> +        }
> >> +
> >> +        default:
> >> +            error_report("%s: Unknown tag 0x%"PRIx64, vbasedev->name, data);
> >> +            return -EINVAL;
> >> +        }
> >> +
> >> +        data = qemu_get_be64(f);
> >> +        ret = qemu_file_get_error(f);
> >> +        if (ret) {
> >> +            return ret;
> >> +        }
> >> +    }
> >> +
> >> +    return ret;
> >> +}
> >> +
> >>   static SaveVMHandlers savevm_vfio_handlers = {
> >>       .save_setup = vfio_save_setup,
> >>       .save_cleanup = vfio_save_cleanup,
> >>       .save_live_pending = vfio_save_pending,
> >>       .save_live_iterate = vfio_save_iterate,
> >>       .save_live_complete_precopy = vfio_save_complete_precopy,
> >> +    .load_setup = vfio_load_setup,
> >> +    .load_cleanup = vfio_load_cleanup,
> >> +    .load_state = vfio_load_state,
> >>   };
> >>   
> >>   /* ---------------------------------------------------------------------- */
> >> diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
> >> index 9a1c5e17d97f..4a4bd3ba9a2a 100644
> >> --- a/hw/vfio/trace-events
> >> +++ b/hw/vfio/trace-events
> >> @@ -157,3 +157,6 @@ vfio_save_device_config_state(const char *name) " (%s)"
> >>   vfio_save_pending(const char *name, uint64_t precopy, uint64_t postcopy, uint64_t compatible) " (%s) precopy 0x%"PRIx64" postcopy 0x%"PRIx64" compatible 0x%"PRIx64
> >>   vfio_save_iterate(const char *name, int data_size) " (%s) data_size %d"
> >>   vfio_save_complete_precopy(const char *name) " (%s)"
> >> +vfio_load_device_config_state(const char *name) " (%s)"
> >> +vfio_load_state(const char *name, uint64_t data) " (%s) data 0x%"PRIx64
> >> +vfio_load_state_device_data(const char *name, uint64_t data_offset, uint64_t data_size) " (%s) Offset 0x%"PRIx64" size 0x%"PRIx64  
> >   
>