Re: [PATCH 4/7] vfio: iommu_type1: Fix missing dirty page when promote pinned_scope

Alex Williamson
2020-12-15T00:06:51Z

On Thu, 10 Dec 2020 15:34:22 +0800
Keqian Zhu <zhukeqian1@huawei.com> wrote:

> When we pin or detach a group which is not dirty tracking capable,
> we will try to promote pinned_scope of vfio_iommu.
>
> If we succeed to do so, vfio only report pinned_scope as dirty to
> userspace next time, but these memory written before pin or detach
> is missed.
>
> The solution is that we must populate all dma range as dirty before
> promoting pinned_scope of vfio_iommu.

Please don't bury fixes patches into a series with other optimizations
and semantic changes. Send it separately.

>
> Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
> ---
> drivers/vfio/vfio_iommu_type1.c | 18 ++++++++++++++++++
> 1 file changed, 18 insertions(+)
>
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index bd9a94590ebc..00684597b098 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -1633,6 +1633,20 @@ static struct vfio_group *vfio_iommu_find_iommu_group(struct vfio_iommu *iommu,
> return group;
> }
>
> +static void vfio_populate_bitmap_all(struct vfio_iommu *iommu)
> +{
> + struct rb_node *n;
> + unsigned long pgshift = __ffs(iommu->pgsize_bitmap);
> +
> + for (n = rb_first(&iommu->dma_list); n; n = rb_next(n)) {
> + struct vfio_dma *dma = rb_entry(n, struct vfio_dma, node);
> + unsigned long nbits = dma->size >> pgshift;
> +
> + if (dma->iommu_mapped)
> + bitmap_set(dma->bitmap, 0, nbits);
> + }
> +}

If we detach a group which results in only non-IOMMU backed mdevs,
don't we also clear dma->iommu_mapped as part of vfio_unmap_unpin()
such that this test is invalid? Thanks,

Alex

> +
> static void promote_pinned_page_dirty_scope(struct vfio_iommu *iommu)
> {
> struct vfio_domain *domain;
> @@ -1657,6 +1671,10 @@ static void promote_pinned_page_dirty_scope(struct vfio_iommu *iommu)
> }
>
> iommu->pinned_page_dirty_scope = true;
> +
> + /* Set all bitmap to avoid missing dirty page */
> + if (iommu->dirty_page_tracking)
> + vfio_populate_bitmap_all(iommu);
> }
>
> static bool vfio_iommu_has_sw_msi(struct list_head *group_resv_regions,