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authorJason Cai (Xiang Feng) <jason.cai@linux.alibaba.com>2018-03-22 12:52:16 +0800
committerAlex Williamson <alex.williamson@redhat.com>2018-03-22 13:18:27 -0600
commit356e88ebe4473a3663cf3d14727ce293a4526d34 (patch)
treee261e27c7ed605750677e610ae7d66dec2d1157c /drivers/vfio
parentc9f89c3f87cfc026d88c08054710902dd52a7772 (diff)
downloadlinux-356e88ebe4473a3663cf3d14727ce293a4526d34.tar.bz2
vfio/type1: Improve memory pinning process for raw PFN mapping
When using vfio to pass through a PCIe device (e.g. a GPU card) that has a huge BAR (e.g. 16GB), a lot of cycles are wasted on memory pinning because PFNs of PCI BAR are not backed by struct page, and the corresponding VMA has flag VM_PFNMAP. With this change, when pinning a region which is a raw PFN mapping, it can skip unnecessary user memory pinning process, and thus, can significantly improve VM's boot up time when passing through devices via VFIO. In my test on a Xeon E5 2.6GHz, the time mapping a 16GB BAR was reduced from about 0.4s to 1.5us. Signed-off-by: Jason Cai (Xiang Feng) <jason.cai@linux.alibaba.com> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Diffstat (limited to 'drivers/vfio')
-rw-r--r--drivers/vfio/vfio_iommu_type1.c25
1 files changed, 15 insertions, 10 deletions
diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 3c082451ab1a..5c212bf29640 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -404,7 +404,6 @@ 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 */
@@ -415,14 +414,23 @@ 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 (!rsvd && !vfio_find_vpfn(dma, iova)) {
+ if (!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__,
@@ -442,13 +450,12 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,
if (ret)
break;
- if (pfn != *pfn_base + pinned ||
- rsvd != is_invalid_reserved_pfn(pfn)) {
+ if (pfn != *pfn_base + pinned) {
put_pfn(pfn, dma->prot);
break;
}
- if (!rsvd && !vfio_find_vpfn(dma, iova)) {
+ if (!vfio_find_vpfn(dma, iova)) {
if (!lock_cap &&
current->mm->locked_vm + lock_acct + 1 > limit) {
put_pfn(pfn, dma->prot);
@@ -466,10 +473,8 @@ out:
unpin_out:
if (ret) {
- if (!rsvd) {
- for (pfn = *pfn_base ; pinned ; pfn++, pinned--)
- put_pfn(pfn, dma->prot);
- }
+ for (pfn = *pfn_base ; pinned ; pfn++, pinned--)
+ put_pfn(pfn, dma->prot);
return ret;
}