[PATCH v4 2/2] vfio/type1: Prune vfio_pin_page_external()

Alex Williamson
2017-04-17T01:42:39Z

With vfio_lock_acct() testing the locked memory limit under mmap_sem,
it's redundant to do it here for a single page. We can also reorder
our tests such that we can avoid testing for reserved pages if we're
not doing accounting, and test the process CAP_IPC_LOCK only if we
are doing accounting. Finally, this function oddly returns 1 on
success. Update to return zero on success, -errno on error. Since
the function only pins a single page, there's no need to return the
number of pages pinned.

N.B. vfio_pin_pages_remote() can pin a large contiguous range of pages
before calling vfio_lock_acct(). If we were to similarly remove the
extra test there, a user could temporarily pin far more pages than
they're allowed.

Suggested-by: Kirti Wankhede <kwankhede@nvidia.com>
Suggested-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
drivers/vfio/vfio_iommu_type1.c | 34 +++++-----------------------------
1 file changed, 5 insertions(+), 29 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index fb18e4a5df62..07e0e58f22e9 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -479,43 +479,21 @@ static long vfio_unpin_pages_remote(struct vfio_dma *dma, dma_addr_t iova,
static int vfio_pin_page_external(struct vfio_dma *dma, unsigned long vaddr,
unsigned long *pfn_base, bool do_accounting)
{
- unsigned long limit;
- bool lock_cap = has_capability(dma->task, CAP_IPC_LOCK);
struct mm_struct *mm;
int ret;
- bool rsvd;

mm = get_task_mm(dma->task);
if (!mm)
return -ENODEV;

ret = vaddr_get_pfn(mm, vaddr, dma->prot, pfn_base);
- if (ret)
- goto pin_page_exit;
-
- rsvd = is_invalid_reserved_pfn(*pfn_base);
- limit = task_rlimit(dma->task, RLIMIT_MEMLOCK) >> PAGE_SHIFT;
-
- if (!rsvd && !lock_cap && mm->locked_vm + 1 > limit) {
- put_pfn(*pfn_base, dma->prot);
- pr_warn("%s: Task %s (%d) RLIMIT_MEMLOCK (%ld) exceeded\n",
- __func__, dma->task->comm, task_pid_nr(dma->task),
- limit << PAGE_SHIFT);
- ret = -ENOMEM;
- goto pin_page_exit;
- }
-
- if (!rsvd && do_accounting) {
- ret = vfio_lock_acct(dma->task, 1, lock_cap);
- if (ret) {
+ if (!ret && do_accounting && !is_invalid_reserved_pfn(*pfn_base)) {
+ ret = vfio_lock_acct(dma->task, 1,
+ has_capability(dma->task, CAP_IPC_LOCK));
+ if (ret)
put_pfn(*pfn_base, dma->prot);
- goto pin_page_exit;
- }
}

- ret = 1;
-
-pin_page_exit:
mmput(mm);
return ret;
}
@@ -595,10 +573,8 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
remote_vaddr = dma->vaddr + iova - dma->iova;
ret = vfio_pin_page_external(dma, remote_vaddr, &phys_pfn[i],
do_accounting);
- if (ret <= 0) {
- WARN_ON(!ret);
+ if (ret)
goto pin_unwind;
- }

ret = vfio_add_to_pfn_list(dma, iova, phys_pfn[i]);
if (ret) {