# Commit 59a5061723ba47c0028cf48487e5de551c42a378
# Date 2015-11-02 15:33:38 +0100
# Author Andrew Cooper <andrew.cooper3@citrix.com>
# Committer Jan Beulich <jbeulich@suse.com>
x86/PoD: Make p2m_pod_empty_cache() restartable

This avoids a long running operation when destroying a domain with a
large PoD cache.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: George Dunlap <george.dunlap@citrix.com>

--- a/xen/arch/x86/mm/p2m-pod.c
+++ b/xen/arch/x86/mm/p2m-pod.c
@@ -375,11 +375,11 @@ out:
     return ret;
 }
 
-void
-p2m_pod_empty_cache(struct domain *d)
+int p2m_pod_empty_cache(struct domain *d)
 {
     struct p2m_domain *p2m = p2m_get_hostp2m(d);
     struct page_info *page;
+    unsigned int i;
 
     /* After this barrier no new PoD activities can happen. */
     BUG_ON(!d->is_dying);
@@ -389,8 +389,6 @@ p2m_pod_empty_cache(struct domain *d)
 
     while ( (page = page_list_remove_head(&p2m->pod.super)) )
     {
-        int i;
-            
         for ( i = 0 ; i < SUPERPAGE_PAGES ; i++ )
         {
             BUG_ON(page_get_owner(page + i) != d);
@@ -398,19 +396,27 @@ p2m_pod_empty_cache(struct domain *d)
         }
 
         p2m->pod.count -= SUPERPAGE_PAGES;
+
+        if ( hypercall_preempt_check() )
+            goto out;
     }
 
-    while ( (page = page_list_remove_head(&p2m->pod.single)) )
+    for ( i = 0; (page = page_list_remove_head(&p2m->pod.single)); ++i )
     {
         BUG_ON(page_get_owner(page) != d);
         page_list_add_tail(page, &d->page_list);
 
         p2m->pod.count -= 1;
+
+        if ( i && !(i & 511) && hypercall_preempt_check() )
+            goto out;
     }
 
     BUG_ON(p2m->pod.count != 0);
 
+ out:
     unlock_page_alloc(p2m);
+    return p2m->pod.count ? -ERESTART : 0;
 }
 
 int
--- a/xen/arch/x86/mm/paging.c
+++ b/xen/arch/x86/mm/paging.c
@@ -815,7 +815,7 @@ int paging_teardown(struct domain *d)
         return rc;
 
     /* Move populate-on-demand cache back to domain_list for destruction */
-    p2m_pod_empty_cache(d);
+    rc = p2m_pod_empty_cache(d);
 
     return rc;
 }
--- a/xen/include/asm-x86/p2m.h
+++ b/xen/include/asm-x86/p2m.h
@@ -588,7 +588,7 @@ void p2m_pod_dump_data(struct domain *d)
 
 /* Move all pages from the populate-on-demand cache to the domain page_list
  * (usually in preparation for domain destruction) */
-void p2m_pod_empty_cache(struct domain *d);
+int p2m_pod_empty_cache(struct domain *d);
 
 /* Set populate-on-demand cache size so that the total memory allocated to a
  * domain matches target */