Re: [PULL v3 15/32] vfio: Add ioctl to get dirty pages bitmap during dma unmap

[zhukeqian]

Hi Kirti,

On 2020/11/2 5:01, Alex Williamson wrote:
> From: Kirti Wankhede <kwankhede@nvidia.com>
> 
> 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 those dirty.
> 
> Suggested-by: Alex Williamson <alex.williamson@redhat.com>
> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
> Reviewed-by: Neo Jia <cjia@nvidia.com>
> [aw: fix error_report types, fix cpu_physical_memory_set_dirty_lebitmap() 
> cast]
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> ---
>  hw/vfio/common.c |   97 
> ++++++++++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 93 insertions(+), 4 deletions(-)
> 
[...]

> +
> +    unmap->argsz = sizeof(*unmap) + sizeof(*bitmap);
> +    unmap->iova = iova;
> +    unmap->size = size;
> +    unmap->flags |= VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP;
> +    bitmap = (struct vfio_bitmap *)&unmap->data;
> +
> +    /*
> +     * cpu_physical_memory_set_dirty_lebitmap() expects pages in bitmap of
> +     * TARGET_PAGE_SIZE to mark those dirty. Hence set bitmap_pgsize to
> +     * TARGET_PAGE_SIZE.
> +     */

Here maybe not OK. cpu_physical_memory_set_dirty_lebitmap expects the granule
of bitmap is qemu_real_host_page_size. It uses hpratio to covert this bitmap
to QEMU dirty bitmap.

Thanks,
Keqian