On Tue, 13 Dec 2022 15:37:45 -0500
Steven Sistare <steven.sistare@xxxxxxxxxx> wrote:
> On 12/13/2022 3:22 PM, Alex Williamson wrote:
> > 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")
>
> will do in both patches, slipped through the cracks.
>
> >> 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.
>
> I added the three WARN_ON's at your request, but they should never fire because
> we exclude mdevs. I prefer not to bloat the code with additional checking that
> never fires, and I would prefer to just delete WARN_ON, but its your call.
Other than convention, what prevents non-mdev code from using this
interface? I agree that making vaddr unmapping and emulated IOMMU
devices mutually exclusive *should* be enough, but I have reason to
suspect there could be out-of-tree non-mdev drivers using these
interfaces. Thanks,
Alex
> >> 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.
>
> I would like to delete the WARN_ON's entirely.
>
> >> 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.
>
> Will do.
>
> >> +
> >> 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,
>
> Another one that should never happen.
>
> - Steve
>
> >> *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;
> >
>
