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@aepfle.de>

diff --git a/tools/xenpaging/xenpaging.c b/tools/xenpaging/xenpaging.c
index 59ba8d32f641969407bfb49070cfc99bafebdd63..dd346db9a6e4e472d69a79c135967bb6083457d4 100644 (file)
--- a/tools/xenpaging/xenpaging.c
+++ b/tools/xenpaging/xenpaging.c
@@ -385,7 +385,7 @@ int xenpaging_evict_page(xc_interface *xch, xenpaging_t *paging,
     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(xenpaging_t *paging, mem_event_response_t *rsp)
         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");