Re: [PATCH QEMU v22 09/18] vfio: Add save state functions to SaveVMHandlers

[Yan Zhao]

On Mon, May 18, 2020 at 11:43:09AM +0530, Kirti Wankhede wrote:

<...>
> +
> +static int vfio_save_buffer(QEMUFile *f, VFIODevice *vbasedev)
> +{
> +    VFIOMigration *migration = vbasedev->migration;
> +    VFIORegion *region = &migration->region;
> +    uint64_t data_offset = 0, data_size = 0;
> +    int ret;
> +
> +    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;
> +    }
> +
> +    ret = pread(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 get migration buffer data size %d",
> +                     vbasedev->name, ret);
> +        return -EINVAL;
> +    }
> +
> +    if (data_size > 0) {
> +        void *buf = NULL;
> +        bool buffer_mmaped;
> +
> +        if (region->mmaps) {
> +            buf = find_data_region(region, data_offset, data_size);
> +        }
> +
> +        buffer_mmaped = (buf != NULL);
> +
> +        if (!buffer_mmaped) {
> +            buf = g_try_malloc(data_size);
> +            if (!buf) {
> +                error_report("%s: Error allocating buffer ", __func__);
> +                return -ENOMEM;
> +            }
> +
> +            ret = pread(vbasedev->fd, buf, data_size,
> +                        region->fd_offset + data_offset);
> +            if (ret != data_size) {
> +                error_report("%s: Failed to get migration data %d",
> +                             vbasedev->name, ret);
> +                g_free(buf);
> +                return -EINVAL;
> +            }
> +        }
> +
> +        qemu_put_be64(f, data_size);
> +        qemu_put_buffer(f, buf, data_size);
> +
> +        if (!buffer_mmaped) {
> +            g_free(buf);
> +        }
> +    } else {
> +        qemu_put_be64(f, data_size);
> +    }
> +
> +    trace_vfio_save_buffer(vbasedev->name, data_offset, data_size,
> +                           migration->pending_bytes);
> +
> +    ret = qemu_file_get_error(f);
> +    if (ret) {
> +        return ret;
> +    }
> +
> +    return data_size;
> +}
> +
> +static int vfio_update_pending(VFIODevice *vbasedev)
> +{
> +    VFIOMigration *migration = vbasedev->migration;
> +    VFIORegion *region = &migration->region;
> +    uint64_t pending_bytes = 0;
> +    int ret;
> +
> +    ret = pread(vbasedev->fd, &pending_bytes, sizeof(pending_bytes),
> +                region->fd_offset + offsetof(struct 
> vfio_device_migration_info,
> +                                             pending_bytes));
> +    if ((ret < 0) || (ret != sizeof(pending_bytes))) {
> +        error_report("%s: Failed to get pending bytes %d",
> +                     vbasedev->name, ret);
> +        migration->pending_bytes = 0;
> +        return (ret < 0) ? ret : -EINVAL;
> +    }
> +
> +    migration->pending_bytes = pending_bytes;
> +    trace_vfio_update_pending(vbasedev->name, pending_bytes);
> +    return 0;
> +}
> +
<...>
>  
> +static void vfio_save_pending(QEMUFile *f, void *opaque,
> +                              uint64_t threshold_size,
> +                              uint64_t *res_precopy_only,
> +                              uint64_t *res_compatible,
> +                              uint64_t *res_postcopy_only)
> +{
> +    VFIODevice *vbasedev = opaque;
> +    VFIOMigration *migration = vbasedev->migration;
> +    int ret;
> +
> +    ret = vfio_update_pending(vbasedev);
> +    if (ret) {
> +        return;
> +    }
> +
> +    *res_precopy_only += migration->pending_bytes;
> +
> +    trace_vfio_save_pending(vbasedev->name, *res_precopy_only,
> +                            *res_postcopy_only, *res_compatible);
> +}
> +
> +static int vfio_save_iterate(QEMUFile *f, void *opaque)
> +{
> +    VFIODevice *vbasedev = opaque;
> +    VFIOMigration *migration = vbasedev->migration;
> +    int ret, data_size;
> +
> +    qemu_put_be64(f, VFIO_MIG_FLAG_DEV_DATA_STATE);
> +
hi Kirti
seems you also didn't address my previous comments.
https://lists.gnu.org/archive/html/qemu-devel/2020-05/msg02795.html.
https://lists.gnu.org/archive/html/qemu-devel/2020-05/msg02796.html


> +    if (migration->pending_bytes == 0) {
> +        ret = vfio_update_pending(vbasedev);
repeated get pending_bytes here would cause vmstats following vfio-pci
have no chance to get called.

Thanks
Yan

> +        if (ret) {
> +            return ret;
> +        }
> +
> +        if (migration->pending_bytes == 0) {
> +            /* indicates data finished, goto complete phase */
> +            return 1;
> +        }
> +    }
> +
> +    data_size = vfio_save_buffer(f, vbasedev);
> +
> +    if (data_size < 0) {
> +        error_report("%s: vfio_save_buffer failed %s", vbasedev->name,
> +                     strerror(errno));
> +        return data_size;
> +    }
> +
> +    qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE);
> +
> +    ret = qemu_file_get_error(f);
> +    if (ret) {
> +        return ret;
> +    }
> +
> +    trace_vfio_save_iterate(vbasedev->name, data_size);
> +
> +    return 0;
> +}
> +

<...>