Re: [PATCH v3 08/13] vfio/common: Add device dirty page tracking start/stop

[Joao Martins]

On 06/03/2023 18:42, Alex Williamson wrote:
> On Sat,  4 Mar 2023 01:43:38 +0000
> Joao Martins <joao.m.martins@oracle.com> wrote:
> 
>> Add device dirty page tracking start/stop functionality. This uses the
>> device DMA logging uAPI to start and stop dirty page tracking by device.
>>
>> Device dirty page tracking is used only if all devices within a
>> container support device dirty page tracking.
>>
>> Signed-off-by: Avihai Horon <avihaih@nvidia.com>
>> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
>> ---
>>  hw/vfio/common.c              | 166 +++++++++++++++++++++++++++++++++-
>>  hw/vfio/trace-events          |   1 +
>>  include/hw/vfio/vfio-common.h |   2 +
>>  3 files changed, 166 insertions(+), 3 deletions(-)
>>
>> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
>> index d84e5fd86bb4..aa0df0604704 100644
>> --- a/hw/vfio/common.c
>> +++ b/hw/vfio/common.c
>> @@ -453,6 +453,22 @@ static bool 
>> vfio_devices_all_dirty_tracking(VFIOContainer *container)
>>      return true;
>>  }
>>  
>> +static bool vfio_devices_all_device_dirty_tracking(VFIOContainer *container)
>> +{
>> +    VFIOGroup *group;
>> +    VFIODevice *vbasedev;
>> +
>> +    QLIST_FOREACH(group, &container->group_list, container_next) {
>> +        QLIST_FOREACH(vbasedev, &group->device_list, next) {
>> +            if (!vbasedev->dirty_pages_supported) {
>> +                return false;
>> +            }
>> +        }
>> +    }
>> +
>> +    return true;
>> +}
>> +
>>  /*
>>   * Check if all VFIO devices are running and migration is active, which is
>>   * essentially equivalent to the migration being in pre-copy phase.
>> @@ -1395,15 +1411,152 @@ static void vfio_dirty_tracking_init(VFIOContainer 
>> *container)
>>      qemu_mutex_destroy(&container->tracking_mutex);
>>  }
>>  
>> +static int vfio_devices_dma_logging_set(VFIOContainer *container,
>> +                                        struct vfio_device_feature *feature)
>> +{
>> +    bool status = (feature->flags & VFIO_DEVICE_FEATURE_MASK) ==
>> +                  VFIO_DEVICE_FEATURE_DMA_LOGGING_START;
>> +    VFIODevice *vbasedev;
>> +    VFIOGroup *group;
>> +    int ret = 0;
>> +
>> +    QLIST_FOREACH(group, &container->group_list, container_next) {
>> +        QLIST_FOREACH(vbasedev, &group->device_list, next) {
>> +            if (vbasedev->dirty_tracking == status) {
>> +                continue;
>> +            }
>> +
>> +            ret = ioctl(vbasedev->fd, VFIO_DEVICE_FEATURE, feature);
>> +            if (ret) {
>> +                ret = -errno;
>> +                error_report("%s: Failed to set DMA logging %s, err %d 
>> (%s)",
>> +                             vbasedev->name, status ? "start" : "stop", ret,
>> +                             strerror(errno));
>> +                goto out;
>> +            }
> 
> Exiting and returning an error on the first failure when starting dirty
> tracking makes sense.  Does that behavior still make sense for the stop
> path?  Maybe since we only support a single device it doesn't really
> matter, but this needs to be revisited for multiple devices.  Thanks,
> 

How about I test for @status and exit earlier based on that?
(maybe variable should be renamed too) e.g.

if (ret) {
  ret = -errno;
  error_report("%s: Failed to set DMA logging %s, err %d (%s)",
               vbasedev->name, status ? "start" : "stop", ret,
               strerror(errno))
  if (status) {
      goto out;
  }
}

> Alex
> 
>> +            vbasedev->dirty_tracking = status;
>> +        }
>> +    }
>> +
>> +out:
>> +    return ret;
>> +}
>> +
>> +static int vfio_devices_dma_logging_stop(VFIOContainer *container)
>> +{
>> +    uint64_t buf[DIV_ROUND_UP(sizeof(struct vfio_device_feature),
>> +                              sizeof(uint64_t))] = {};
>> +    struct vfio_device_feature *feature = (struct vfio_device_feature *)buf;
>> +
>> +    feature->argsz = sizeof(buf);
>> +    feature->flags = VFIO_DEVICE_FEATURE_SET;
>> +    feature->flags |= VFIO_DEVICE_FEATURE_DMA_LOGGING_STOP;
>> +
>> +    return vfio_devices_dma_logging_set(container, feature);
>> +}
>> +
>> +static struct vfio_device_feature *
>> +vfio_device_feature_dma_logging_start_create(VFIOContainer *container)
>> +{
>> +    struct vfio_device_feature *feature;
>> +    size_t feature_size;
>> +    struct vfio_device_feature_dma_logging_control *control;
>> +    struct vfio_device_feature_dma_logging_range *ranges;
>> +    VFIODirtyTrackingRange *tracking = &container->tracking_range;
>> +
>> +    feature_size = sizeof(struct vfio_device_feature) +
>> +                   sizeof(struct vfio_device_feature_dma_logging_control);
>> +    feature = g_try_malloc0(feature_size);
>> +    if (!feature) {
>> +        errno = ENOMEM;
>> +        return NULL;
>> +    }
>> +    feature->argsz = feature_size;
>> +    feature->flags = VFIO_DEVICE_FEATURE_SET;
>> +    feature->flags |= VFIO_DEVICE_FEATURE_DMA_LOGGING_START;
>> +
>> +    control = (struct vfio_device_feature_dma_logging_control 
>> *)feature->data;
>> +    control->page_size = qemu_real_host_page_size();
>> +
>> +    /*
>> +     * DMA logging uAPI guarantees to support at least a number of ranges 
>> that
>> +     * fits into a single host kernel base page.
>> +     */
>> +    control->num_ranges = !!tracking->max32 + !!tracking->max64;
>> +    ranges = g_try_new0(struct vfio_device_feature_dma_logging_range,
>> +                        control->num_ranges);
>> +    if (!ranges) {
>> +        g_free(feature);
>> +        errno = ENOMEM;
>> +
>> +        return NULL;
>> +    }
>> +
>> +    control->ranges = (__aligned_u64)ranges;
>> +    if (tracking->max32) {
>> +        ranges->iova = tracking->min32;
>> +        ranges->length = (tracking->max32 - tracking->min32) + 1;
>> +        ranges++;
>> +    }
>> +    if (tracking->max64) {
>> +        ranges->iova = tracking->min64;
>> +        ranges->length = (tracking->max64 - tracking->min64) + 1;
>> +    }
>> +
>> +    trace_vfio_device_dirty_tracking_start(control->num_ranges,
>> +                                           tracking->min32, tracking->max32,
>> +                                           tracking->min64, 
>> tracking->max64);
>> +
>> +    return feature;
>> +}
>> +
>> +static void vfio_device_feature_dma_logging_start_destroy(
>> +    struct vfio_device_feature *feature)
>> +{
>> +    struct vfio_device_feature_dma_logging_control *control =
>> +        (struct vfio_device_feature_dma_logging_control *)feature->data;
>> +    struct vfio_device_feature_dma_logging_range *ranges =
>> +        (struct vfio_device_feature_dma_logging_range *)control->ranges;
>> +
>> +    g_free(ranges);
>> +    g_free(feature);
>> +}
>> +
>> +static int vfio_devices_dma_logging_start(VFIOContainer *container)
>> +{
>> +    struct vfio_device_feature *feature;
>> +    int ret = 0;
>> +
>> +    vfio_dirty_tracking_init(container);
>> +    feature = vfio_device_feature_dma_logging_start_create(container);
>> +    if (!feature) {
>> +        return -errno;
>> +    }
>> +
>> +    ret = vfio_devices_dma_logging_set(container, feature);
>> +    if (ret) {
>> +        vfio_devices_dma_logging_stop(container);
>> +    }
>> +
>> +    vfio_device_feature_dma_logging_start_destroy(feature);
>> +
>> +    return ret;
>> +}
>> +
>>  static void vfio_listener_log_global_start(MemoryListener *listener)
>>  {
>>      VFIOContainer *container = container_of(listener, VFIOContainer, 
>> listener);
>>      int ret;
>>  
>> -    vfio_dirty_tracking_init(container);
>> +    if (vfio_devices_all_device_dirty_tracking(container)) {
>> +        ret = vfio_devices_dma_logging_start(container);
>> +    } else {
>> +        ret = vfio_set_dirty_page_tracking(container, true);
>> +    }
>>  
>> -    ret = vfio_set_dirty_page_tracking(container, true);
>>      if (ret) {
>> +        error_report("vfio: Could not start dirty page tracking, err: %d 
>> (%s)",
>> +                     ret, strerror(-ret));
>>          vfio_set_migration_error(ret);
>>      }
>>  }
>> @@ -1413,8 +1566,15 @@ static void 
>> vfio_listener_log_global_stop(MemoryListener *listener)
>>      VFIOContainer *container = container_of(listener, VFIOContainer, 
>> listener);
>>      int ret;
>>  
>> -    ret = vfio_set_dirty_page_tracking(container, false);
>> +    if (vfio_devices_all_device_dirty_tracking(container)) {
>> +        ret = vfio_devices_dma_logging_stop(container);
>> +    } else {
>> +        ret = vfio_set_dirty_page_tracking(container, false);
>> +    }
>> +
>>      if (ret) {
>> +        error_report("vfio: Could not stop dirty page tracking, err: %d 
>> (%s)",
>> +                     ret, strerror(-ret));
>>          vfio_set_migration_error(ret);
>>      }
>>  }
>> diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
>> index d97a6de17921..7a7e0cfe5b23 100644
>> --- a/hw/vfio/trace-events
>> +++ b/hw/vfio/trace-events
>> @@ -105,6 +105,7 @@ vfio_listener_region_add_no_dma_map(const char *name, 
>> uint64_t iova, uint64_t si
>>  vfio_listener_region_del_skip(uint64_t start, uint64_t end) "SKIPPING 
>> region_del 0x%"PRIx64" - 0x%"PRIx64
>>  vfio_listener_region_del(uint64_t start, uint64_t end) "region_del 
>> 0x%"PRIx64" - 0x%"PRIx64
>>  vfio_device_dirty_tracking_update(uint64_t start, uint64_t end, uint64_t 
>> min, uint64_t max) "section 0x%"PRIx64" - 0x%"PRIx64" -> update [0x%"PRIx64" 
>> - 0x%"PRIx64"]"
>> +vfio_device_dirty_tracking_start(int nr_ranges, uint64_t min32, uint64_t 
>> max32, uint64_t min64, uint64_t max64) "nr_ranges %d 32:[0x%"PRIx64" - 
>> 0x%"PRIx64"], 64:[0x%"PRIx64" - 0x%"PRIx64"]"
>>  vfio_disconnect_container(int fd) "close container->fd=%d"
>>  vfio_put_group(int fd) "close group->fd=%d"
>>  vfio_get_device(const char * name, unsigned int flags, unsigned int 
>> num_regions, unsigned int num_irqs) "Device %s flags: %u, regions: %u, irqs: 
>> %u"
>> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
>> index 96791add2719..1cbbccd91e11 100644
>> --- a/include/hw/vfio/vfio-common.h
>> +++ b/include/hw/vfio/vfio-common.h
>> @@ -154,6 +154,8 @@ typedef struct VFIODevice {
>>      VFIOMigration *migration;
>>      Error *migration_blocker;
>>      OnOffAuto pre_copy_dirty_page_tracking;
>> +    bool dirty_pages_supported;
>> +    bool dirty_tracking;
>>  } VFIODevice;
>>  
>>  struct VFIODeviceOps {
>