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

[Joao Martins]

On 06/03/2023 20:00, Alex Williamson wrote:
> On Mon, 6 Mar 2023 19:39:15 +0000
> Joao Martins <joao.m.martins@oracle.com> wrote:
> 
>> 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;
>>   }
>> }
> 
> Yep, exit on first error enabling, continue on disabling makes more
> sense, but then we need to look at what return code makes sense for the
> teardown.  TBH, a teardown function would typically return void, so
> it's possible we'd be better off not using this for both.  Thanks,
> 
Agreed. I can unroll set into _start and _stop and turn _stop into a void 
function.

> Alex
> 
> PS - no further original comments on v3 from me.
> 
OK

>>>> +            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 {  
>>>   
>>
>