Re: [PATCH v9 QEMU 14/15] vfio: Add ioctl to get dirty pages bitmap during dma unmap.

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

On Tue, 12 Nov 2019 22:35:23 +0530
Kirti Wankhede <kwankhede@nvidia.com> wrote:

> With vIOMMU, IO virtual address range can get unmapped while in pre-copy phase
> of migration. In that case, unmap ioctl should return pages pinned in that range
> and QEMU should find its correcponding guest physical addresses and report

corresponding

> those dirty.
> 
> Note: This patch is not yet tested. I'm trying to see how I can test this code
> path.
> 
> Suggested-by: Alex Williamson <alex.williamson@redhat.com>
> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
> Reviewed-by: Neo Jia <cjia@nvidia.com>
> ---
>  hw/vfio/common.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 61 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 66f1c64bf074..dc5768219d44 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -311,11 +311,30 @@ static bool vfio_devices_are_stopped_and_saving(void)
>      return true;
>  }
>  
> +static bool vfio_devices_are_running_and_saving(void)
> +{
> +    VFIOGroup *group;
> +    VFIODevice *vbasedev;
> +
> +    QLIST_FOREACH(group, &vfio_group_list, next) {
> +        QLIST_FOREACH(vbasedev, &group->device_list, next) {
> +            if ((vbasedev->device_state & VFIO_DEVICE_STATE_SAVING) &&
> +                (vbasedev->device_state & VFIO_DEVICE_STATE_RUNNING)) {
> +                continue;
> +            } else {
> +                return false;
> +            }
> +        }
> +    }
> +    return true;
> +}

Suggests to generalize the other function to allow the caller to
provide the mask and value to test for.

> +
>  /*
>   * DMA - Mapping and unmapping for the "type1" IOMMU interface used on x86
>   */
>  static int vfio_dma_unmap(VFIOContainer *container,
> -                          hwaddr iova, ram_addr_t size)
> +                          hwaddr iova, ram_addr_t size,
> +                          VFIOGuestIOMMU *giommu)
>  {
>      struct vfio_iommu_type1_dma_unmap unmap = {
>          .argsz = sizeof(unmap),
> @@ -324,6 +343,44 @@ static int vfio_dma_unmap(VFIOContainer *container,
>          .size = size,
>      };
>  
> +    if (giommu && vfio_devices_are_running_and_saving()) {
> +        int ret;
> +        uint64_t bitmap_size;
> +        struct vfio_iommu_type1_dma_unmap_bitmap unmap_bitmap = {
> +            .argsz = sizeof(unmap_bitmap),
> +            .flags = VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP,
> +            .iova = iova,
> +            .size = size,
> +        };
> +
> +        bitmap_size = BITS_TO_LONGS(size >> TARGET_PAGE_BITS) *
> +                      sizeof(uint64_t);
> +
> +        unmap_bitmap.bitmap = g_try_malloc0(bitmap_size);
> +        if (!unmap_bitmap.bitmap) {
> +            error_report("%s: Error allocating bitmap buffer of size 0x%lx",
> +                         __func__, bitmap_size);
> +            return -ENOMEM;
> +        }
> +
> +        unmap_bitmap.bitmap_size = bitmap_size;
> +
> +        ret = ioctl(container->fd, VFIO_IOMMU_UNMAP_DMA_GET_BITMAP,
> +                    &unmap_bitmap);
> +
> +        if (!ret) {
> +            cpu_physical_memory_set_dirty_lebitmap(
> +                                        (uint64_t *)unmap_bitmap.bitmap,
> +                                        giommu->iommu_offset + giommu->n.start,
> +                                        bitmap_size >> TARGET_PAGE_BITS);

+1 Yan's comments.

> +        } else {
> +            error_report("VFIO_IOMMU_GET_DIRTY_BITMAP: %d %d", ret, errno);
> +        }
> +
> +        g_free(unmap_bitmap.bitmap);
> +        return ret;
> +    }
> +
>      while (ioctl(container->fd, VFIO_IOMMU_UNMAP_DMA, &unmap)) {
>          /*
>           * The type1 backend has an off-by-one bug in the kernel (71a7d3d78e3c
> @@ -371,7 +428,7 @@ static int vfio_dma_map(VFIOContainer *container, hwaddr iova,
>       * the VGA ROM space.
>       */
>      if (ioctl(container->fd, VFIO_IOMMU_MAP_DMA, &map) == 0 ||
> -        (errno == EBUSY && vfio_dma_unmap(container, iova, size) == 0 &&
> +        (errno == EBUSY && vfio_dma_unmap(container, iova, size, NULL) == 0 &&
>           ioctl(container->fd, VFIO_IOMMU_MAP_DMA, &map) == 0)) {
>          return 0;
>      }
> @@ -511,7 +568,7 @@ static void vfio_iommu_map_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
>                           iotlb->addr_mask + 1, vaddr, ret);
>          }
>      } else {
> -        ret = vfio_dma_unmap(container, iova, iotlb->addr_mask + 1);
> +        ret = vfio_dma_unmap(container, iova, iotlb->addr_mask + 1, giommu);
>          if (ret) {
>              error_report("vfio_dma_unmap(%p, 0x%"HWADDR_PRIx", "
>                           "0x%"HWADDR_PRIx") = %d (%m)",
> @@ -814,7 +871,7 @@ static void vfio_listener_region_del(MemoryListener *listener,
>      }
>  
>      if (try_unmap) {
> -        ret = vfio_dma_unmap(container, iova, int128_get64(llsize));
> +        ret = vfio_dma_unmap(container, iova, int128_get64(llsize), NULL);
>          if (ret) {
>              error_report("vfio_dma_unmap(%p, 0x%"HWADDR_PRIx", "
>                           "0x%"HWADDR_PRIx") = %d (%m)",