On Tue, 13 Dec 2022 11:40:55 -0800
Steve Sistare <steven.sistare@xxxxxxxxxx> wrote:
> Disable the VFIO_UPDATE_VADDR capability if mediated devices are present.
> Their kernel threads could be blocked indefinitely by a misbehaving
> userland while trying to pin/unpin pages while vaddrs are being updated.
>
> Do not allow groups to be added to the container while vaddr's are invalid,
> so we never need to block user threads from pinning, and can delete the
> vaddr-waiting code in a subsequent patch.
>
Fixes: c3cbab24db38 ("vfio/type1: implement interfaces to update vaddr")
> Signed-off-by: Steve Sistare <steven.sistare@xxxxxxxxxx>
> ---
> drivers/vfio/vfio_iommu_type1.c | 31 ++++++++++++++++++++++++++++++-
> include/uapi/linux/vfio.h | 15 +++++++++------
> 2 files changed, 39 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 23c24fe..80bdb4d 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -859,6 +859,8 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
> if (!iommu->v2)
> return -EACCES;
>
> + WARN_ON(iommu->vaddr_invalid_count);
> +
I'd expect this to abort and return -errno rather than simply trigger a
warning.
> mutex_lock(&iommu->lock);
>
> /*
> @@ -976,6 +978,8 @@ static void vfio_iommu_type1_unpin_pages(void *iommu_data,
>
> mutex_lock(&iommu->lock);
>
> + WARN_ON(iommu->vaddr_invalid_count);
> +
This should never happen or else I'd suggest this also make an early
exit.
> do_accounting = list_empty(&iommu->domain_list);
> for (i = 0; i < npage; i++) {
> dma_addr_t iova = user_iova + PAGE_SIZE * i;
> @@ -1343,6 +1347,10 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
>
> mutex_lock(&iommu->lock);
>
> + /* Cannot update vaddr if mdev is present. */
> + if (invalidate_vaddr && !list_empty(&iommu->emulated_iommu_groups))
> + goto unlock;
A different errno here to reflect that the container state is the issue
might be appropriate here.
> +
> pgshift = __ffs(iommu->pgsize_bitmap);
> pgsize = (size_t)1 << pgshift;
>
> @@ -2189,6 +2197,10 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
>
> mutex_lock(&iommu->lock);
>
> + /* Attach could require pinning, so disallow while vaddr is invalid. */
> + if (iommu->vaddr_invalid_count)
> + goto out_unlock;
> +
> /* Check for duplicates */
> if (vfio_iommu_find_iommu_group(iommu, iommu_group))
> goto out_unlock;
> @@ -2660,6 +2672,16 @@ static int vfio_domains_have_enforce_cache_coherency(struct vfio_iommu *iommu)
> return ret;
> }
>
> +static int vfio_iommu_has_emulated(struct vfio_iommu *iommu)
> +{
> + int ret;
> +
> + mutex_lock(&iommu->lock);
> + ret = !list_empty(&iommu->emulated_iommu_groups);
> + mutex_unlock(&iommu->lock);
> + return ret;
> +}
> +
> static int vfio_iommu_type1_check_extension(struct vfio_iommu *iommu,
> unsigned long arg)
> {
> @@ -2668,8 +2690,13 @@ static int vfio_iommu_type1_check_extension(struct vfio_iommu *iommu,
> case VFIO_TYPE1v2_IOMMU:
> case VFIO_TYPE1_NESTING_IOMMU:
> case VFIO_UNMAP_ALL:
> - case VFIO_UPDATE_VADDR:
> return 1;
> + case VFIO_UPDATE_VADDR:
> + /*
> + * Disable this feature if mdevs are present. They cannot
> + * safely pin/unpin while vaddrs are being updated.
> + */
> + return iommu && !vfio_iommu_has_emulated(iommu);
> case VFIO_DMA_CC_IOMMU:
> if (!iommu)
> return 0;
> @@ -3080,6 +3107,8 @@ static int vfio_iommu_type1_dma_rw_chunk(struct vfio_iommu *iommu,
> size_t offset;
> int ret;
>
> + WARN_ON(iommu->vaddr_invalid_count);
> +
Same as pinning, this should trigger -errno. Thanks,
Alex
> *copied = 0;
>
> ret = vfio_find_dma_valid(iommu, user_iova, 1, &dma);
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index d7d8e09..4e8d344 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -49,7 +49,11 @@
> /* Supports VFIO_DMA_UNMAP_FLAG_ALL */
> #define VFIO_UNMAP_ALL 9
>
> -/* Supports the vaddr flag for DMA map and unmap */
> +/*
> + * Supports the vaddr flag for DMA map and unmap. Not supported for mediated
> + * devices, so this capability is subject to change as groups are added or
> + * removed.
> + */
> #define VFIO_UPDATE_VADDR 10
>
> /*
> @@ -1215,8 +1219,7 @@ struct vfio_iommu_type1_info_dma_avail {
> * Map process virtual addresses to IO virtual addresses using the
> * provided struct vfio_dma_map. Caller sets argsz. READ &/ WRITE required.
> *
> - * If flags & VFIO_DMA_MAP_FLAG_VADDR, update the base vaddr for iova, and
> - * unblock translation of host virtual addresses in the iova range. The vaddr
> + * If flags & VFIO_DMA_MAP_FLAG_VADDR, update the base vaddr for iova. The vaddr
> * must have previously been invalidated with VFIO_DMA_UNMAP_FLAG_VADDR. To
> * maintain memory consistency within the user application, the updated vaddr
> * must address the same memory object as originally mapped. Failure to do so
> @@ -1267,9 +1270,9 @@ struct vfio_bitmap {
> * must be 0. This cannot be combined with the get-dirty-bitmap flag.
> *
> * If flags & VFIO_DMA_UNMAP_FLAG_VADDR, do not unmap, but invalidate host
> - * virtual addresses in the iova range. Tasks that attempt to translate an
> - * iova's vaddr will block. DMA to already-mapped pages continues. This
> - * cannot be combined with the get-dirty-bitmap flag.
> + * virtual addresses in the iova range. DMA to already-mapped pages continues.
> + * Groups may not be added to the container while any addresses are invalid.
> + * This cannot be combined with the get-dirty-bitmap flag.
> */
> struct vfio_iommu_type1_dma_unmap {
> __u32 argsz;
