Re: [PATCH v16 QEMU 10/16] vfio: Add load state functions to SaveVMHandlers

[Kirti Wankhede]

On 4/2/2020 12:28 AM, Dr. David Alan Gilbert wrote:
> * Kirti Wankhede (address@hidden) 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 <address@hidden>
> > Reviewed-by: Neo Jia <address@hidden>
> > ---
> >   hw/vfio/migration.c  | 179 +++++++++++++++++++++++++++++++++++++++++++++++++++
> >   hw/vfio/trace-events |   3 +
> >   2 files changed, 182 insertions(+)
> >
> > diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
> > index ecbeed5182c2..ab295d25620e 100644
> > --- a/hw/vfio/migration.c
> > +++ b/hw/vfio/migration.c
> > @@ -269,6 +269,33 @@ 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)
> > @@ -434,12 +461,164 @@ 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;
> > +        }
> > +    }
> > +
> > +    ret = vfio_migration_set_state(vbasedev, ~0, 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:
> > +        {
> > +            uint64_t region_size = qemu_get_be64(f);
> > +
> > +            if (migration->region.size < region_size) {
> > +                error_report("%s: SETUP STATE: migration region too small, "
> > +                             "0x%"PRIx64 " < 0x%"PRIx64, vbasedev->name,
> > +                             migration->region.size, region_size);
> > +                return -EINVAL;
> > +            }
> > +
> > +            data = qemu_get_be64(f);
> > +            if (data == VFIO_MIG_FLAG_END_OF_STATE) {
>
> Can you explain why you're reading this here rather than letting it drop
> through to the read at the end of the loop?

To make sure sequence is followed, otherwise throw error.

> > +                return ret;
> > +            } else {
> > +                error_report("%s: SETUP STATE: EOS not found 0x%"PRIx64,
> > +                             vbasedev->name, data);
> > +                return -EINVAL;
> > +            }
> > +            break;
> > +        }
> > +        case VFIO_MIG_FLAG_DEV_DATA_STATE:
> > +        {
> > +            VFIORegion *region = &migration->region;
> > +            void *buf = NULL;
> > +            bool buffer_mmaped = false;
> > +            uint64_t data_offset = 0;
> > +
> > +            data_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;
> > +            }
> > +
> > +            if (region->mmaps) {
> > +                buf = find_data_region(region, data_offset, data_size);
> > +            }
> > +
> > +            buffer_mmaped = (buf != NULL) ? true : false;
> > +
> > +            if (!buffer_mmaped) {
> > +                buf = g_try_malloc0(data_size);
>
> data_size has been read off the wire at this point; can we sanity check
> it?

I do added a check above (data_size == 0), but here sanity check with what?

Thanks,
Kirti

> > +                if (!buf) {
> > +                    error_report("%s: Error allocating buffer ", __func__);
> > +                    return -ENOMEM;
> > +                }
> > +            }
> > +
> > +            qemu_get_buffer(f, buf, data_size);
> > +
> > +            if (!buffer_mmaped) {
> > +                ret = pwrite(vbasedev->fd, buf, data_size,
> > +                             region->fd_offset + data_offset);
> > +                g_free(buf);
> > +
> > +                if (ret != data_size) {
> > +                    error_report("%s: Failed to set migration buffer %d",
> > +                                 vbasedev->name, ret);
> > +                    return -EINVAL;
> > +                }
> > +            }
> > +
> > +            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);
> > +                if (!buffer_mmaped) {
> > +                    g_free(buf);
> > +                }
> > +                return -EINVAL;
> > +            }
> > +
> > +            trace_vfio_load_state_device_data(vbasedev->name, data_offset,
> > +                                              data_size);
> > +            break;
> > +        }
>
> I'd add here a default:  that complains about an unknown tag.
>
> > +        }
> > +
> > +        ret = qemu_file_get_error(f);
> > +        if (ret) {
> > +            return ret;
> > +        }
> > +        data = qemu_get_be64(f);
>
> I'd also check file_get_error again at this point; if you're unlucky you
> get junk in 'data' and things get more confusing.
>
> > +    }
> > +
> > +    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 bdf40ba368c7..ac065b559f4e 100644
> > --- a/hw/vfio/trace-events
> > +++ b/hw/vfio/trace-events
> > @@ -157,3 +157,6 @@ vfio_save_device_config_state(char *name) " (%s)"
> >   vfio_save_pending(char *name, uint64_t precopy, uint64_t postcopy, uint64_t compatible) " (%s) precopy 
> > 0x%"PRIx64" postcopy 0x%"PRIx64" compatible 0x%"PRIx64
> >   vfio_save_iterate(char *name, int data_size) " (%s) data_size %d"
> >   vfio_save_complete_precopy(char *name) " (%s)"
> > +vfio_load_device_config_state(char *name) " (%s)"
> > +vfio_load_state(char *name, uint64_t data) " (%s) data 0x%"PRIx64
>
> Please use const char*'s in traces.
>
> > +vfio_load_state_device_data(char *name, uint64_t data_offset, uint64_t data_size) " (%s) 
> > Offset 0x%"PRIx64" size 0x%"PRIx64
> > --
> > 2.7.0
> --
> Dr. David Alan Gilbert / address@hidden / Manchester, UK