[PATCH 3.12 28/39] xen/gntdev: Grant maps should not be subject to NUMA balancing

From: Jiri Slaby
Date: Mon Jan 25 2016 - 06:51:51 EST

From: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>

3.12-stable review patch. If anyone has any objections, please let me know.


commit 9c17d96500f78d7ecdb71ca6942830158bc75a2b upstream.

Doing so will cause the grant to be unmapped and then, during
fault handling, the fault to be mistakenly treated as NUMA hint

In addition, even if those maps could partcipate in NUMA
balancing, it wouldn't provide any benefit since we are unable
to determine physical page's node (even if/when VNUMA is

Marking grant maps' VMAs as VM_IO will exclude them from being
part of NUMA balancing.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
drivers/xen/gntdev.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index 0b5806995718..27accc4cc999 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -763,7 +763,7 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma)

vma->vm_ops = &gntdev_vmops;

- vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
+ vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP | VM_IO;

if (use_ptemod)
vma->vm_flags |= VM_DONTCOPY;