[Xen-changelog] [xen-unstable] xenpaging: notify policy only on resume

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir@xxxxxxx>
# Date 1290781210 0
# Node ID 7d2c013727d756e5c50726d9d55f108b006197dd
# Parent  1b87fbd10f437da95d35c861b4989af5460e2796
xenpaging: notify policy only on resume

If a page is requested more than once, the policy is also notified
more than once about the page-in. However, a page-in happens only
once. Any further resume will only unpause the other vcpu. The
multiple notify will put the page into the mru list multiple times and
it will unlock other already resumed pages too early. In the worst
case, a page that was just resumed can be evicted right away, causing
a deadlock in the guest.

Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>
---
 tools/xenpaging/xenpaging.c |    9 +++++----
 1 files changed, 5 insertions(+), 4 deletions(-)

diff -r 1b87fbd10f43 -r 7d2c013727d7 tools/xenpaging/xenpaging.c
--- a/tools/xenpaging/xenpaging.c       Fri Nov 26 14:19:38 2010 +0000
+++ b/tools/xenpaging/xenpaging.c       Fri Nov 26 14:20:10 2010 +0000
@@ -385,7 +385,7 @@ int xenpaging_evict_page(xc_interface *x
     return ret;
 }
 
-static int xenpaging_resume_page(xenpaging_t *paging, mem_event_response_t 
*rsp)
+static int xenpaging_resume_page(xenpaging_t *paging, mem_event_response_t 
*rsp, int notify_policy)
 {
     int ret;
 
@@ -395,7 +395,8 @@ static int xenpaging_resume_page(xenpagi
         goto out;
 
     /* Notify policy of page being paged in */
-    policy_notify_paged_in(paging->mem_event.domain_id, rsp->gfn);
+    if ( notify_policy )
+        policy_notify_paged_in(paging->mem_event.domain_id, rsp->gfn);
 
     /* Tell Xen page is ready */
     ret = xc_mem_paging_resume(paging->xc_handle, paging->mem_event.domain_id,
@@ -621,7 +622,7 @@ int main(int argc, char *argv[])
                 rsp.vcpu_id = req.vcpu_id;
                 rsp.flags = req.flags;
 
-                rc = xenpaging_resume_page(paging, &rsp);
+                rc = xenpaging_resume_page(paging, &rsp, 1);
                 if ( rc != 0 )
                 {
                     ERROR("Error resuming page");
@@ -650,7 +651,7 @@ int main(int argc, char *argv[])
                     rsp.vcpu_id = req.vcpu_id;
                     rsp.flags = req.flags;
 
-                    rc = xenpaging_resume_page(paging, &rsp);
+                    rc = xenpaging_resume_page(paging, &rsp, 0);
                     if ( rc != 0 )
                     {
                         ERROR("Error resuming");

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