I just realized it makes more sense to directly count dma->locked_vm, which
can be done with a few lines in vfio_lock_acct. I will do that tomorrow,
along with addressing any new comments from this review.
- Steve
On 12/15/2022 4:57 PM, Steve Sistare wrote:
> A pinned dma mapping may include reserved pages, which are not included
> in the task's locked_vm count. Maintain a count of reserved pages, for
> iommu capable devices, so that locked_vm can be restored after fork or
> exec in a subsequent patch.
>
> Signed-off-by: Steve Sistare <steven.sistare@xxxxxxxxxx>
> ---
> drivers/vfio/vfio_iommu_type1.c | 14 +++++++++++---
> 1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index cd49b656..add87cd 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -101,6 +101,7 @@ struct vfio_dma {
> struct rb_root pfn_list; /* Ex-user pinned pfn list */
> unsigned long *bitmap;
> struct mm_struct *mm;
> + long reserved_pages;
> };
>
> struct vfio_batch {
> @@ -662,7 +663,7 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,
> {
> unsigned long pfn;
> struct mm_struct *mm = current->mm;
> - long ret, pinned = 0, lock_acct = 0;
> + long ret, pinned = 0, lock_acct = 0, reserved_pages = 0;
> bool rsvd;
> dma_addr_t iova = vaddr - dma->vaddr + dma->iova;
>
> @@ -716,7 +717,9 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,
> * externally pinned pages are already counted against
> * the user.
> */
> - if (!rsvd && !vfio_find_vpfn(dma, iova)) {
> + if (rsvd) {
> + reserved_pages++;
> + } else if (!vfio_find_vpfn(dma, iova)) {
> if (!dma->lock_cap &&
> mm->locked_vm + lock_acct + 1 > limit) {
> pr_warn("%s: RLIMIT_MEMLOCK (%ld) exceeded\n",
> @@ -746,6 +749,8 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,
>
> out:
> ret = vfio_lock_acct(dma, lock_acct, false);
> + if (!ret)
> + dma->reserved_pages += reserved_pages;
>
> unpin_out:
> if (batch->size == 1 && !batch->offset) {
> @@ -771,7 +776,7 @@ static long vfio_unpin_pages_remote(struct vfio_dma *dma, dma_addr_t iova,
> unsigned long pfn, long npage,
> bool do_accounting)
> {
> - long unlocked = 0, locked = 0;
> + long unlocked = 0, locked = 0, reserved_pages = 0;
> long i;
>
> for (i = 0; i < npage; i++, iova += PAGE_SIZE) {
> @@ -779,9 +784,12 @@ static long vfio_unpin_pages_remote(struct vfio_dma *dma, dma_addr_t iova,
> unlocked++;
> if (vfio_find_vpfn(dma, iova))
> locked++;
> + } else {
> + reserved_pages++;
> }
> }
>
> + dma->reserved_pages -= reserved_pages;
> if (do_accounting)
> vfio_lock_acct(dma, locked - unlocked, true);
>
