Re: [PATCH 11/18] vfio/common: Add device dirty page bitmap sync

[Alex Williamson <alex.williamson@redhat.com>]

On Thu, 26 Jan 2023 20:49:41 +0200
Avihai Horon <avihaih@nvidia.com> wrote:

> From: Joao Martins <joao.m.martins@oracle.com>
> 
> Add device dirty page bitmap sync functionality. This uses the device
> DMA logging uAPI to sync dirty page bitmap from the device.
> 
> Device dirty page bitmap sync is used only if all devices within a
> container support device dirty page tracking.
> 
> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
> Signed-off-by: Avihai Horon <avihaih@nvidia.com>
> ---
>  hw/vfio/common.c | 93 ++++++++++++++++++++++++++++++++++++++++++------
>  1 file changed, 82 insertions(+), 11 deletions(-)
> 
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 3caa73d6f7..0003f2421d 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -355,6 +355,9 @@ static void vfio_bitmap_dealloc(VFIOBitmap *vbmap)
>      g_free(vbmap);
>  }
>  
> +static int vfio_get_dirty_bitmap(VFIOContainer *container, uint64_t iova,
> +                                 uint64_t size, ram_addr_t ram_addr);
> +
>  bool vfio_mig_active(void)
>  {
>      VFIOGroup *group;
> @@ -582,10 +585,19 @@ static int vfio_dma_unmap(VFIOContainer *container,
>          .iova = iova,
>          .size = size,
>      };
> +    int ret;
>  
> -    if (iotlb && container->dirty_pages_supported &&
> -        vfio_devices_all_running_and_mig_active(container)) {
> -        return vfio_dma_unmap_bitmap(container, iova, size, iotlb);
> +    if (iotlb && vfio_devices_all_running_and_mig_active(container)) {
> +        if (!vfio_devices_all_device_dirty_tracking(container) &&
> +            container->dirty_pages_supported) {
> +            return vfio_dma_unmap_bitmap(container, iova, size, iotlb);
> +        }
> +
> +        ret = vfio_get_dirty_bitmap(container, iova, size,
> +                                    iotlb->translated_addr);
> +        if (ret) {
> +            return ret;
> +        }

Isn't the ordering backwards here?  Only after the range is unmapped
can we know that this container can no longer dirty pages within the
range.  Thanks,

Alex