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

[Alex Williamson]

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,

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 {