On 12/13/2022 3:59 PM, Alex Williamson wrote:
> 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,
OK, none of the exclusion checks will prevent such calls, even for mdevs. I will
delete the WARN_ON's and return an error code.
- Steve
>>>> 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;
>>>
>>
>
