x86/mm: Check how many mfns are shared, in addition to how many are saved

This patch also moves the existing sharing-related memory op to the
correct location, and adds logic to the audit() method that uses the
new information.

This patch only provides the Xen implementation of the domctls.

Signed-off-by: Andres Lagar-Cavilla <andres@scannell.ca>
Signed-off-by: Adin Scannell <adin@scannell.ca>
Acked-by: Tim Deegan <tim@xen.org>
Committed-by: Tim Deegan <tim@xen.org>

xen/arch/x86/mm.c

@@ -119,7 +119,6 @@
 #include <xen/trace.h>
 #include <asm/setup.h>
 #include <asm/fixmap.h>
-#include <asm/mem_sharing.h>
 
 /*
  * Mapping of first 2 or 4 megabytes of memory. This is mapped with 4kB
@@ -5023,11 +5022,6 @@ long arch_memory_op(int op, XEN_GUEST_HANDLE(void) arg)
         return rc;
     }
 
-#ifdef __x86_64__
-    case XENMEM_get_sharing_freed_pages:
-        return mem_sharing_get_nr_saved_mfns();
-#endif
-
     default:
         return subarch_memory_op(op, arg);
     }

xen/arch/x86/mm/mem_sharing.c

@@ -138,6 +138,7 @@ static inline shr_handle_t get_next_handle(void)
 #define page_to_mfn(_pg) _mfn(__page_to_mfn(_pg))
 
 static atomic_t nr_saved_mfns   = ATOMIC_INIT(0); 
+static atomic_t nr_shared_mfns  = ATOMIC_INIT(0);
 
 typedef struct gfn_info
 {
@@ -208,9 +209,12 @@ static struct page_info* mem_sharing_lookup(unsigned long mfn)
 static void mem_sharing_audit(void)
 {
     int errors = 0;
+    unsigned long count_expected;
+    unsigned long count_found = 0;
     struct list_head *ae;
 
     ASSERT(shr_locked_by_me());
+    count_expected = atomic_read(&nr_shared_mfns);
 
     list_for_each(ae, &shr_audit_list)
     {
@@ -258,6 +262,9 @@ static void mem_sharing_audit(void)
            continue;
         }
 
+        /* We've found a page that is shared */
+        count_found++;
+
         /* Check if all GFNs map to the MFN, and the p2m types */
         list_for_each(le, &pg->shared_info->gfns)
         {
@@ -302,6 +309,14 @@ static void mem_sharing_audit(void)
             errors++;
         }
     }
+
+    if ( count_found != count_expected )
+    {
+        MEM_SHARING_DEBUG("Expected %ld shared mfns, found %ld.",
+                          count_expected, count_found);
+        errors++;
+    }
+
 }
 #endif
 
@@ -342,6 +357,11 @@ unsigned int mem_sharing_get_nr_saved_mfns(void)
     return ((unsigned int)atomic_read(&nr_saved_mfns));
 }
 
+unsigned int mem_sharing_get_nr_shared_mfns(void)
+{
+    return (unsigned int)atomic_read(&nr_shared_mfns);
+}
+
 int mem_sharing_sharing_resume(struct domain *d)
 {
     mem_event_response_t rsp;
@@ -663,6 +683,9 @@ int mem_sharing_nominate_page(struct domain *d,
         goto out;
     }
 
+    /* Account for this page. */
+    atomic_inc(&nr_shared_mfns);
+
     /* Update m2p entry to SHARED_M2P_ENTRY */
     set_gpfn_from_mfn(mfn_x(mfn), SHARED_M2P_ENTRY);
 
@@ -786,6 +809,7 @@ int mem_sharing_share_pages(struct domain *sd, unsigned long sgfn, shr_handle_t
         put_page(cpage);
 
     /* We managed to free a domain page. */
+    atomic_dec(&nr_shared_mfns);
     atomic_inc(&nr_saved_mfns);
     ret = 0;
     
@@ -851,6 +875,7 @@ gfn_found:
         audit_del_list(page);
         xfree(page->shared_info);
         page->shared_info = NULL;
+        atomic_dec(&nr_shared_mfns);
     }
     else
         atomic_dec(&nr_saved_mfns);

xen/arch/x86/x86_64/compat/mm.c

@@ -205,6 +205,12 @@ int compat_arch_memory_op(int op, XEN_GUEST_HANDLE(void) arg)
         break;
     }
 
+    case XENMEM_get_sharing_freed_pages:
+        return mem_sharing_get_nr_saved_mfns();
+
+    case XENMEM_get_sharing_shared_pages:
+        return mem_sharing_get_nr_shared_mfns();
+
     default:
         rc = -ENOSYS;
         break;

xen/arch/x86/x86_64/mm.c

@@ -34,6 +34,7 @@
 #include <asm/msr.h>
 #include <asm/setup.h>
 #include <asm/numa.h>
+#include <asm/mem_sharing.h>
 #include <public/memory.h>
 
 /* Parameters for PFN/MADDR compression. */
@@ -1093,6 +1094,12 @@ long subarch_memory_op(int op, XEN_GUEST_HANDLE(void) arg)
 
         break;
 
+    case XENMEM_get_sharing_freed_pages:
+        return mem_sharing_get_nr_saved_mfns();
+
+    case XENMEM_get_sharing_shared_pages:
+        return mem_sharing_get_nr_shared_mfns();
+
     default:
         rc = -ENOSYS;
         break;

xen/include/asm-x86/mem_sharing.h

@@ -45,6 +45,7 @@ struct page_sharing_info
     (is_hvm_domain(_d) && paging_mode_hap(_d)) 
 
 unsigned int mem_sharing_get_nr_saved_mfns(void);
+unsigned int mem_sharing_get_nr_shared_mfns(void);
 int mem_sharing_nominate_page(struct domain *d, 
                               unsigned long gfn,
                               int expected_refcnt,

xen/include/public/memory.h

@@ -294,6 +294,7 @@ typedef struct xen_pod_target xen_pod_target_t;
  * The call never fails. 
  */
 #define XENMEM_get_sharing_freed_pages    18
+#define XENMEM_get_sharing_shared_pages   19
 
 #endif /* __XEN_PUBLIC_MEMORY_H__ */