[PATCH 4 of 9] x86/mm: Check how many mfns are shared, in addition to how many are saved

[Andres Lagar-Cavilla <andres@lagarcavilla.org>]

 xen/arch/x86/mm.c                 |   6 ------
 xen/arch/x86/mm/mem_sharing.c     |  29 +++++++++++++++++++++++++++++
 xen/arch/x86/x86_64/compat/mm.c   |   6 ++++++
 xen/arch/x86/x86_64/mm.c          |   7 +++++++
 xen/include/asm-x86/mem_sharing.h |   1 +
 xen/include/public/memory.h       |   1 +
 6 files changed, 44 insertions(+), 6 deletions(-)


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>

diff -r 4a189125d71e -r dbfabd1bbfb1 xen/arch/x86/mm.c
--- a/xen/arch/x86/mm.c
+++ b/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
@@ -5093,11 +5092,6 @@ long arch_memory_op(int op, XEN_GUEST_HA
         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);
     }
diff -r 4a189125d71e -r dbfabd1bbfb1 xen/arch/x86/mm/mem_sharing.c
--- a/xen/arch/x86/mm/mem_sharing.c
+++ b/xen/arch/x86/mm/mem_sharing.c
@@ -72,6 +72,7 @@ static inline int mem_sharing_audit(void
 
 static shr_handle_t next_handle = 1;
 static atomic_t nr_saved_mfns   = ATOMIC_INIT(0); 
+static atomic_t nr_shared_mfns  = ATOMIC_INIT(0);
 
 typedef struct gfn_info
 {
@@ -150,9 +151,12 @@ static struct page_info* mem_sharing_loo
 static int 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)
     {
@@ -200,6 +204,10 @@ static int mem_sharing_audit(void)
            continue;
         }
 
+        /* Only increase our expected count for pages that are actually shared */
+        if ( !list_has_one_entry(&pg->shared_info->gfns) )
+            count_found++;
+
         /* Check if all GFNs map to the MFN, and the p2m types */
         list_for_each(le, &pg->shared_info->gfns)
         {
@@ -245,6 +253,13 @@ static int mem_sharing_audit(void)
         }
     }
 
+    if ( count_found != count_expected )
+    {
+        MEM_SHARING_DEBUG("Expected %ld shared mfns, found %ld.",
+                          count_expected, count_found);
+        errors++;
+    }
+
     return errors;
 }
 #endif
@@ -294,6 +309,11 @@ unsigned int mem_sharing_get_nr_saved_mf
     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;
@@ -577,6 +597,14 @@ int mem_sharing_share_pages(struct domai
     ASSERT(list_empty(&cpage->shared_info->gfns));
     if ( single_source_gfn )
         atomic_inc(&sd->shr_pages);
+    /* We only increase the number of shared pages when 
+     * sharing for the first time */
+    if ( single_source_gfn && single_client_gfn )
+        atomic_inc(&nr_shared_mfns);
+    /* And we decrease it when re-sharing already shared
+     * (because one of them becomes a "saved" page). */
+    if ( !single_source_gfn && !single_client_gfn )
+        atomic_dec(&nr_shared_mfns);
 
     /* Clear the rest of the shared state */
     audit_del_list(cpage);
@@ -659,6 +687,7 @@ gfn_found:
             BUG_ON(!d);
             atomic_dec(&d->shr_pages);
             put_domain(d);
+            atomic_dec(&nr_shared_mfns);
         }
     } else {
         /* Clean up shared state */
diff -r 4a189125d71e -r dbfabd1bbfb1 xen/arch/x86/x86_64/compat/mm.c
--- a/xen/arch/x86/x86_64/compat/mm.c
+++ b/xen/arch/x86/x86_64/compat/mm.c
@@ -205,6 +205,12 @@ int compat_arch_memory_op(int op, XEN_GU
         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;
diff -r 4a189125d71e -r dbfabd1bbfb1 xen/arch/x86/x86_64/mm.c
--- a/xen/arch/x86/x86_64/mm.c
+++ b/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. */
@@ -1090,6 +1091,12 @@ long subarch_memory_op(int op, XEN_GUEST
 
         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;
diff -r 4a189125d71e -r dbfabd1bbfb1 xen/include/asm-x86/mem_sharing.h
--- a/xen/include/asm-x86/mem_sharing.h
+++ b/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,
diff -r 4a189125d71e -r dbfabd1bbfb1 xen/include/public/memory.h
--- a/xen/include/public/memory.h
+++ b/xen/include/public/memory.h
@@ -294,6 +294,7 @@ typedef struct xen_pod_target xen_pod_ta
  * The call never fails. 
  */
 #define XENMEM_get_sharing_freed_pages    18
+#define XENMEM_get_sharing_shared_pages   19
 
 #endif /* __XEN_PUBLIC_MEMORY_H__ */