Commit 356e88eb authored by Jason Cai (Xiang Feng)'s avatar Jason Cai (Xiang Feng) Committed by Alex Williamson

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: default avatarJason Cai (Xiang Feng) <jason.cai@linux.alibaba.com>
Signed-off-by: default avatarAlex Williamson <alex.williamson@redhat.com>
parent c9f89c3f
...@@ -404,7 +404,6 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr, ...@@ -404,7 +404,6 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,
{ {
unsigned long pfn = 0; unsigned long pfn = 0;
long ret, pinned = 0, lock_acct = 0; long ret, pinned = 0, lock_acct = 0;
bool rsvd;
dma_addr_t iova = vaddr - dma->vaddr + dma->iova; dma_addr_t iova = vaddr - dma->vaddr + dma->iova;
/* This code path is only user initiated */ /* This code path is only user initiated */
...@@ -415,14 +414,23 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr, ...@@ -415,14 +414,23 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,
if (ret) if (ret)
return 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++; pinned++;
rsvd = is_invalid_reserved_pfn(*pfn_base);
/* /*
* Reserved pages aren't counted against the user, externally pinned * Reserved pages aren't counted against the user, externally pinned
* pages are already counted against the user. * 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) { if (!lock_cap && current->mm->locked_vm + 1 > limit) {
put_pfn(*pfn_base, dma->prot); put_pfn(*pfn_base, dma->prot);
pr_warn("%s: RLIMIT_MEMLOCK (%ld) exceeded\n", __func__, 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, ...@@ -442,13 +450,12 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,
if (ret) if (ret)
break; break;
if (pfn != *pfn_base + pinned || if (pfn != *pfn_base + pinned) {
rsvd != is_invalid_reserved_pfn(pfn)) {
put_pfn(pfn, dma->prot); put_pfn(pfn, dma->prot);
break; break;
} }
if (!rsvd && !vfio_find_vpfn(dma, iova)) { if (!vfio_find_vpfn(dma, iova)) {
if (!lock_cap && if (!lock_cap &&
current->mm->locked_vm + lock_acct + 1 > limit) { current->mm->locked_vm + lock_acct + 1 > limit) {
put_pfn(pfn, dma->prot); put_pfn(pfn, dma->prot);
...@@ -466,10 +473,8 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr, ...@@ -466,10 +473,8 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,
unpin_out: unpin_out:
if (ret) { if (ret) {
if (!rsvd) { for (pfn = *pfn_base ; pinned ; pfn++, pinned--)
for (pfn = *pfn_base ; pinned ; pfn++, pinned--) put_pfn(pfn, dma->prot);
put_pfn(pfn, dma->prot);
}
return ret; return ret;
} }
......
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