[Xen-devel] [PATCH] Input: xen-kbdfront - free grant table entry in xenkbd_disconnect_backend

[hansechang@xxxxxxxxx]

From: Chang Huaixin <huaixin.chx@xxxxxxxxxxxxxxx>

xenkbd_disconnect_backend doesn't free grant table entry.
This bug affects live migration.

xenkbd_disconnect_backend uses gnttab_end_foreign_access_ref
to handle grant table entry which doesn't really free an entry.

Thus every time we do xenkbd_resume, grant table entry increses
by one. As an grant table entry occupies 8 bytes, an grant table
page has at most 512 entries. Every 512 times we do xenkdb_resume,
grant table pages increses by one.

After around 3500 times of live migration, grant table pages
will increase by 7, causing too many pages to populate and hitting
max_pages limit when assigning pages.Thus assign_pages will fail,
so will live migration.

Signed-off-by: Chang Huaixin <huaixin.chx@xxxxxxxxxxxxxxx>
---
 drivers/input/misc/xen-kbdfront.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/input/misc/xen-kbdfront.c 
b/drivers/input/misc/xen-kbdfront.c
index fbfdc10..e2ecfc6 100644
--- a/drivers/input/misc/xen-kbdfront.c
+++ b/drivers/input/misc/xen-kbdfront.c
@@ -285,7 +285,7 @@ static int xenkbd_connect_backend(struct xenbus_device *dev,
  error_evtchan:
        xenbus_free_evtchn(dev, evtchn);
  error_grant:
-       gnttab_end_foreign_access_ref(info->gref, 0);
+       gnttab_end_foreign_access(info->gref, 0, 0UL);
        info->gref = -1;
        return ret;
 }
@@ -296,7 +296,7 @@ static void xenkbd_disconnect_backend(struct xenkbd_info 
*info)
                unbind_from_irqhandler(info->irq, info);
        info->irq = -1;
        if (info->gref >= 0)
-               gnttab_end_foreign_access_ref(info->gref, 0);
+               gnttab_end_foreign_access(info->gref, 0, 0UL);
        info->gref = -1;
 }
 
-- 
1.9.1


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