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

[Kirti Wankhede <kwankhede@nvidia.com>]

On 4/2/2020 12:28 AM, Dr. David Alan Gilbert wrote:
> * 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>
>> ---
>>   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 / dgilbert@redhat.com / Manchester, UK
>