Re: [Qemu-devel] [PATCH 5/5] vfio/migration: support device memory capability

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Yan Zhao (yan.y.zhao@intel.com) wrote:
> If a device has device memory capability, save/load data from device memory
> in pre-copy and stop-and-copy phases.
> 
> LOGGING state is set for device memory for dirty page logging:
> in LOGGING state, get device memory returns whole device memory snapshot;
> outside LOGGING state, get device memory returns dirty data since last get
> operation.
> 
> Usually, device memory is very big, qemu needs to chunk it into several
> pieces each with size of device memory region.
> 
> Signed-off-by: Yan Zhao <yan.y.zhao@intel.com>
> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
> ---
>  hw/vfio/migration.c | 235 ++++++++++++++++++++++++++++++++++++++++++++++++++--
>  hw/vfio/pci.h       |   1 +
>  2 files changed, 231 insertions(+), 5 deletions(-)
> 
> diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
> index 16d6395..f1e9309 100644
> --- a/hw/vfio/migration.c
> +++ b/hw/vfio/migration.c
> @@ -203,6 +203,201 @@ static int vfio_load_data_device_config(VFIOPCIDevice *vdev,
>      return 0;
>  }
>  
> +static int vfio_get_device_memory_size(VFIOPCIDevice *vdev)
> +{
> +    VFIODevice *vbasedev = &vdev->vbasedev;
> +    VFIORegion *region_ctl =
> +        &vdev->migration->region[VFIO_DEVSTATE_REGION_CTL];
> +    uint64_t len;
> +    int sz;
> +
> +    sz = sizeof(len);
> +    if (pread(vbasedev->fd, &len, sz,
> +                region_ctl->fd_offset +
> +                offsetof(struct vfio_device_state_ctl, device_memory.size))
> +            != sz) {
> +        error_report("vfio: Failed to get length of device memory");
> +        return -1;
> +    }
> +    vdev->migration->devmem_size = len;
> +    return 0;
> +}
> +
> +static int vfio_set_device_memory_size(VFIOPCIDevice *vdev, uint64_t size)
> +{
> +    VFIODevice *vbasedev = &vdev->vbasedev;
> +    VFIORegion *region_ctl =
> +        &vdev->migration->region[VFIO_DEVSTATE_REGION_CTL];
> +    int sz;
> +
> +    sz = sizeof(size);
> +    if (pwrite(vbasedev->fd, &size, sz,
> +                region_ctl->fd_offset +
> +                offsetof(struct vfio_device_state_ctl, device_memory.size))
> +            != sz) {
> +        error_report("vfio: Failed to set length of device comemory");
> +        return -1;
> +    }
> +    vdev->migration->devmem_size = size;
> +    return 0;
> +}
> +
> +static
> +int vfio_save_data_device_memory_chunk(VFIOPCIDevice *vdev, QEMUFile *f,
> +                                    uint64_t pos, uint64_t len)
> +{
> +    VFIODevice *vbasedev = &vdev->vbasedev;
> +    VFIORegion *region_ctl =
> +        &vdev->migration->region[VFIO_DEVSTATE_REGION_CTL];
> +    VFIORegion *region_devmem =
> +        &vdev->migration->region[VFIO_DEVSTATE_REGION_DATA_DEVICE_MEMORY];
> +    void *dest;
> +    uint32_t sz;
> +    uint8_t *buf = NULL;
> +    uint32_t action = VFIO_DEVICE_DATA_ACTION_GET_BUFFER;
> +
> +    if (len > region_devmem->size) {
> +        return -1;
> +    }
> +
> +    sz = sizeof(pos);
> +    if (pwrite(vbasedev->fd, &pos, sz,
> +                region_ctl->fd_offset +
> +                offsetof(struct vfio_device_state_ctl, device_memory.pos))
> +            != sz) {
> +        error_report("vfio: Failed to set save buffer pos");
> +        return -1;
> +    }
> +    sz = sizeof(action);
> +    if (pwrite(vbasedev->fd, &action, sz,
> +                region_ctl->fd_offset +
> +                offsetof(struct vfio_device_state_ctl, device_memory.action))
> +            != sz) {
> +        error_report("vfio: Failed to set save buffer action");
> +        return -1;
> +    }
> +
> +    if (!vfio_device_state_region_mmaped(region_devmem)) {
> +        buf = g_malloc(len);
> +        if (buf == NULL) {
> +            error_report("vfio: Failed to allocate memory for migrate");
> +            return -1;
> +        }
> +        if (pread(vbasedev->fd, buf, len, region_devmem->fd_offset) != len) {
> +            error_report("vfio: error load device memory buffer");

That's forgotten to g_free(buf)

> +            return -1;
> +        }
> +        qemu_put_be64(f, len);
> +        qemu_put_be64(f, pos);
> +        qemu_put_buffer(f, buf, len);
> +        g_free(buf);
> +    } else {
> +        dest = region_devmem->mmaps[0].mmap;
> +        qemu_put_be64(f, len);
> +        qemu_put_be64(f, pos);
> +        qemu_put_buffer(f, dest, len);
> +    }
> +    return 0;
> +}
> +
> +static int vfio_save_data_device_memory(VFIOPCIDevice *vdev, QEMUFile *f)
> +{
> +    VFIORegion *region_devmem =
> +        &vdev->migration->region[VFIO_DEVSTATE_REGION_DATA_DEVICE_MEMORY];
> +    uint64_t total_len = vdev->migration->devmem_size;
> +    uint64_t pos = 0;
> +
> +    qemu_put_be64(f, total_len);
> +    while (pos < total_len) {
> +        uint64_t len = region_devmem->size;
> +
> +        if (pos + len >= total_len) {
> +            len = total_len - pos;
> +        }
> +        if (vfio_save_data_device_memory_chunk(vdev, f, pos, len)) {
> +            return -1;
> +        }
> +    }
> +
> +    return 0;
> +}
> +
> +static
> +int vfio_load_data_device_memory_chunk(VFIOPCIDevice *vdev, QEMUFile *f,
> +                                uint64_t pos, uint64_t len)
> +{
> +    VFIODevice *vbasedev = &vdev->vbasedev;
> +    VFIORegion *region_ctl =
> +        &vdev->migration->region[VFIO_DEVSTATE_REGION_CTL];
> +    VFIORegion *region_devmem =
> +        &vdev->migration->region[VFIO_DEVSTATE_REGION_DATA_DEVICE_MEMORY];
> +
> +    void *dest;
> +    uint32_t sz;
> +    uint8_t *buf = NULL;
> +    uint32_t action = VFIO_DEVICE_DATA_ACTION_SET_BUFFER;
> +
> +    if (len > region_devmem->size) {
> +        return -1;
> +    }
> +
> +    sz = sizeof(pos);
> +    if (pwrite(vbasedev->fd, &pos, sz,
> +                region_ctl->fd_offset +
> +                offsetof(struct vfio_device_state_ctl, device_memory.pos))
> +            != sz) {
> +        error_report("vfio: Failed to set device memory buffer pos");
> +        return -1;
> +    }
> +    if (!vfio_device_state_region_mmaped(region_devmem)) {
> +        buf = g_malloc(len);
> +        if (buf == NULL) {
> +            error_report("vfio: Failed to allocate memory for migrate");
> +            return -1;
> +        }
> +        qemu_get_buffer(f, buf, len);
> +        if (pwrite(vbasedev->fd, buf, len,
> +                    region_devmem->fd_offset) != len) {
> +            error_report("vfio: Failed to load devie memory buffer");

Again, failed to free buf

> +            return -1;
> +        }
> +        g_free(buf);
> +    } else {
> +        dest = region_devmem->mmaps[0].mmap;
> +        qemu_get_buffer(f, dest, len);
> +    }

You might want to use qemu_file_get_error(f)  before writing the data
to the device, to check for the case of a read error on the migration
stream that happened somewhere in the pevious qemu_get's

> +    sz = sizeof(action);
> +    if (pwrite(vbasedev->fd, &action, sz,
> +                region_ctl->fd_offset +
> +                offsetof(struct vfio_device_state_ctl, device_memory.action))
> +            != sz) {
> +        error_report("vfio: Failed to set load device memory buffer action");
> +        return -1;
> +    }
> +
> +    return 0;
> +
> +}
> +
> +static int vfio_load_data_device_memory(VFIOPCIDevice *vdev,
> +                        QEMUFile *f, uint64_t total_len)
> +{
> +    uint64_t pos = 0, len = 0;
> +
> +    vfio_set_device_memory_size(vdev, total_len);
> +
> +    while (pos + len < total_len) {
> +        len = qemu_get_be64(f);
> +        pos = qemu_get_be64(f);

Please check len/pos - always assume that the migration stream could
be (maliciously or accidentally) corrupt.

> +        vfio_load_data_device_memory_chunk(vdev, f, pos, len);
> +    }
> +
> +    return 0;
> +}
> +
> +
>  static int vfio_set_dirty_page_bitmap_chunk(VFIOPCIDevice *vdev,
>          uint64_t start_addr, uint64_t page_nr)
>  {
> @@ -377,6 +572,10 @@ static void vfio_save_live_pending(QEMUFile *f, void *opaque,
>          return;
>      }
>  
> +    /* get dirty data size of device memory */
> +    vfio_get_device_memory_size(vdev);
> +
> +    *res_precopy_only += vdev->migration->devmem_size;
>      return;
>  }
>  
> @@ -388,7 +587,9 @@ static int vfio_save_iterate(QEMUFile *f, void *opaque)
>          return 0;
>      }
>  
> -    return 0;
> +    qemu_put_byte(f, VFIO_SAVE_FLAG_DEVMEMORY);
> +    /* get dirty data of device memory */
> +    return vfio_save_data_device_memory(vdev, f);
>  }
>  
>  static void vfio_pci_load_config(VFIOPCIDevice *vdev, QEMUFile *f)
> @@ -458,6 +659,10 @@ static int vfio_load_state(QEMUFile *f, void *opaque, int version_id)
>              len = qemu_get_be64(f);
>              vfio_load_data_device_config(vdev, f, len);
>              break;
> +        case VFIO_SAVE_FLAG_DEVMEMORY:
> +            len = qemu_get_be64(f);
> +            vfio_load_data_device_memory(vdev, f, len);
> +            break;
>          default:
>              ret = -EINVAL;
>          }
> @@ -503,6 +708,13 @@ static int vfio_save_complete_precopy(QEMUFile *f, void *opaque)
>      VFIOPCIDevice *vdev = opaque;
>      int rc = 0;
>  
> +    if (vfio_device_data_cap_device_memory(vdev)) {
> +        qemu_put_byte(f, VFIO_SAVE_FLAG_DEVMEMORY | VFIO_SAVE_FLAG_CONTINUE);
> +        /* get dirty data of device memory */
> +        vfio_get_device_memory_size(vdev);
> +        rc = vfio_save_data_device_memory(vdev, f);
> +    }
> +
>      qemu_put_byte(f, VFIO_SAVE_FLAG_PCI | VFIO_SAVE_FLAG_CONTINUE);
>      vfio_pci_save_config(vdev, f);
>  
> @@ -515,12 +727,22 @@ static int vfio_save_complete_precopy(QEMUFile *f, void *opaque)
>  
>  static int vfio_save_setup(QEMUFile *f, void *opaque)
>  {
> +    int rc = 0;
>      VFIOPCIDevice *vdev = opaque;
> -    qemu_put_byte(f, VFIO_SAVE_FLAG_SETUP);
> +
> +    if (vfio_device_data_cap_device_memory(vdev)) {
> +        qemu_put_byte(f, VFIO_SAVE_FLAG_SETUP | VFIO_SAVE_FLAG_CONTINUE);
> +        qemu_put_byte(f, VFIO_SAVE_FLAG_DEVMEMORY);
> +        /* get whole snapshot of device memory */
> +        vfio_get_device_memory_size(vdev);
> +        rc = vfio_save_data_device_memory(vdev, f);
> +    } else {
> +        qemu_put_byte(f, VFIO_SAVE_FLAG_SETUP);
> +    }
>  
>      vfio_set_device_state(vdev, VFIO_DEVICE_STATE_RUNNING |
>              VFIO_DEVICE_STATE_LOGGING);
> -    return 0;
> +    return rc;
>  }
>  
>  static int vfio_load_setup(QEMUFile *f, void *opaque)
> @@ -576,8 +798,11 @@ int vfio_migration_init(VFIOPCIDevice *vdev, Error **errp)
>          goto error;
>      }
>  
> -    if (vfio_device_data_cap_device_memory(vdev)) {
> -        error_report("No suppport of data cap device memory Yet");
> +    if (vfio_device_data_cap_device_memory(vdev) &&
> +            vfio_device_state_region_setup(vdev,
> +              &vdev->migration->region[VFIO_DEVSTATE_REGION_DATA_DEVICE_MEMORY],
> +              VFIO_REGION_SUBTYPE_DEVICE_STATE_DATA_MEMORY,
> +              "device-state-data-device-memory")) {
>          goto error;
>      }
>  
> diff --git a/hw/vfio/pci.h b/hw/vfio/pci.h
> index 4b7b1bb..a2cc64b 100644
> --- a/hw/vfio/pci.h
> +++ b/hw/vfio/pci.h
> @@ -69,6 +69,7 @@ typedef struct VFIOMigration {
>      uint32_t data_caps;
>      uint32_t device_state;
>      uint64_t devconfig_size;
> +    uint64_t devmem_size;
>      VMChangeStateEntry *vm_state;
>  } VFIOMigration;
>  
> -- 
> 2.7.4
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK