Re: [PATCH v18 QEMU 16/18] vfio: Add ioctl to get dirty pages bitmap during dma unmap.

[Cornelia Huck <cohuck@redhat.com>]

On Tue, 5 May 2020 04:14:51 +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 those dirty.
> 
> Note: This patch is not yet tested. I'm trying to see how I can test this
> code path.

This remark should go beneath the '---' line, so that it does not end
up in the final commit.

> 
> 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 | 79 +++++++++++++++++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 75 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 4277b275ca21..b94e2bcb1178 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -311,11 +311,77 @@ static bool vfio_devices_are_stopped_and_saving(void)
>      return true;
>  }
>  
> +static bool vfio_devices_are_running_and_saving(void)

Maybe s/are/all/ to make it sure that the scope is *all* vfio devices
here?

Is there any global state for this which we could use to check this in
a simpler way?

> +{
> +    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;
> +}
> +
> +static int vfio_dma_unmap_bitmap(VFIOContainer *container,
> +                                 hwaddr iova, ram_addr_t size,
> +                                 IOMMUTLBEntry *iotlb)
> +{
> +    struct vfio_iommu_type1_dma_unmap *unmap;
> +    struct vfio_bitmap *bitmap;
> +    uint64_t pages = TARGET_PAGE_ALIGN(size) >> TARGET_PAGE_BITS;
> +    int ret;
> +
> +    unmap = g_malloc0(sizeof(*unmap) + sizeof(*bitmap));

g_malloc0 cannot fail (it will abort). If you want to be able to
tolerate memory allocation failure, you should use g_try_malloc0().

> +    if (!unmap) {
> +        return -ENOMEM;
> +    }
> +
> +    unmap->argsz = sizeof(*unmap) + sizeof(*bitmap);
> +    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.
> +     */
> +
> +    bitmap->pgsize = TARGET_PAGE_SIZE;
> +    bitmap->size = ROUND_UP(pages / 8, sizeof(uint64_t));
> +    bitmap->data = g_malloc0(bitmap->size);
> +    if (!bitmap->data) {
> +        error_report("UNMAP: Error allocating bitmap of size 0x%llx",
> +                     bitmap->size);
> +        g_free(unmap);
> +        return -ENOMEM;
> +    }
> +
> +    ret = ioctl(container->fd, VFIO_IOMMU_UNMAP_DMA, unmap);
> +    if (!ret) {
> +        cpu_physical_memory_set_dirty_lebitmap((uint64_t *)bitmap->data,
> +                iotlb->translated_addr, pages);
> +    } else {
> +        error_report("VFIO_UNMAP_DMA with DIRTY_BITMAP : %d", -errno);
> +    }
> +
> +    g_free(bitmap->data);
> +    g_free(unmap);
> +    return ret;
> +}
> +