[PATCH] Revert "vfio/type1: Improve memory pinning process for raw PFN mapping"

From: Alex Williamson
Date: Sat Jun 02 2018 - 12:27:07 EST


Bisection by Amadeusz SÅawiÅski implicates this commit leading to bad
page state issues after VM shutdown, likely due to unbalanced page
references. The original commit was intended only as a performance
improvement, therefore revert for offline rework.

Link: https://lkml.org/lkml/2018/6/2/97
Fixes: 356e88ebe447 ("vfio/type1: Improve memory pinning process for raw PFN mapping")
Cc: Jason Cai (Xiang Feng) <jason.cai@xxxxxxxxxxxxxxxxx>
Reported-by: Amadeusz SÅawiÅski <amade@xxxxxxxxxx>
Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
---
drivers/vfio/vfio_iommu_type1.c | 25 ++++++++++---------------
1 file changed, 10 insertions(+), 15 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 5c212bf29640..3c082451ab1a 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -404,6 +404,7 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,
{
unsigned long pfn = 0;
long ret, pinned = 0, lock_acct = 0;
+ bool rsvd;
dma_addr_t iova = vaddr - dma->vaddr + dma->iova;

/* This code path is only user initiated */
@@ -414,23 +415,14 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,
if (ret)
return ret;

- if (is_invalid_reserved_pfn(*pfn_base)) {
- struct vm_area_struct *vma;
-
- down_read(&current->mm->mmap_sem);
- vma = find_vma_intersection(current->mm, vaddr, vaddr + 1);
- pinned = min_t(long, npage, vma_pages(vma));
- up_read(&current->mm->mmap_sem);
- return pinned;
- }
-
pinned++;
+ rsvd = is_invalid_reserved_pfn(*pfn_base);

/*
* Reserved pages aren't counted against the user, externally pinned
* pages are already counted against the user.
*/
- if (!vfio_find_vpfn(dma, iova)) {
+ if (!rsvd && !vfio_find_vpfn(dma, iova)) {
if (!lock_cap && current->mm->locked_vm + 1 > limit) {
put_pfn(*pfn_base, dma->prot);
pr_warn("%s: RLIMIT_MEMLOCK (%ld) exceeded\n", __func__,
@@ -450,12 +442,13 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,
if (ret)
break;

- if (pfn != *pfn_base + pinned) {
+ if (pfn != *pfn_base + pinned ||
+ rsvd != is_invalid_reserved_pfn(pfn)) {
put_pfn(pfn, dma->prot);
break;
}

- if (!vfio_find_vpfn(dma, iova)) {
+ if (!rsvd && !vfio_find_vpfn(dma, iova)) {
if (!lock_cap &&
current->mm->locked_vm + lock_acct + 1 > limit) {
put_pfn(pfn, dma->prot);
@@ -473,8 +466,10 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,

unpin_out:
if (ret) {
- for (pfn = *pfn_base ; pinned ; pfn++, pinned--)
- put_pfn(pfn, dma->prot);
+ if (!rsvd) {
+ for (pfn = *pfn_base ; pinned ; pfn++, pinned--)
+ put_pfn(pfn, dma->prot);
+ }

return ret;
}