x86/mm: Make debug_{gfn, mfn, gref} calls to sharing more useful and correct

Have them used locked accesors to the gfn and the underlying shared mfn.

Have them return the number of shared refs to the underlying mfn.

Signed-off-by: Andres Lagar-Cavilla <andres@lagarcavilla.org>
Acked-by: Tim Deegan <tim@xen.org>
Committed-by: Tim Deegan <tim@xen.org>

1 files changed, 115 insertions, 109 deletions

diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c
index 539c35b6f8..cb35147a48 100644
--- a/xen/arch/x86/mm/mem_sharing.c
+++ b/xen/arch/x86/mm/mem_sharing.c
@@ -45,13 +45,13 @@ typedef struct pg_lock_data {
 
 DEFINE_PER_CPU(pg_lock_data_t, __pld);
 
+#define MEM_SHARING_DEBUG(_f, _a...)                                  \
+    debugtrace_printk("mem_sharing_debug: %s(): " _f, __func__, ##_a)
+
 #if MEM_SHARING_AUDIT
 
 static void mem_sharing_audit(void);
 
-#define MEM_SHARING_DEBUG(_f, _a...)                                  \
-    debugtrace_printk("mem_sharing_debug: %s(): " _f, __func__, ##_a)
-
 static struct list_head shr_audit_list;
 static spinlock_t shr_audit_lock;
 DEFINE_RCU_READ_LOCK(shr_audit_read_lock);
@@ -398,111 +398,6 @@ int mem_sharing_sharing_resume(struct domain *d)
     return 0;
 }
 
-int mem_sharing_debug_mfn(unsigned long mfn)
-{
-    struct page_info *page;
-
-    if ( !mfn_valid(_mfn(mfn)) )
-    {
-        gdprintk(XENLOG_ERR, "Invalid MFN=%lx\n", mfn);
-        return -1;
-    }
-    page = mfn_to_page(_mfn(mfn));
-
-    gdprintk(XENLOG_DEBUG, 
-            "Debug page: MFN=%lx is ci=%lx, ti=%lx, owner_id=%d\n",
-            mfn_x(page_to_mfn(page)), 
-            page->count_info, 
-            page->u.inuse.type_info,
-            page_get_owner(page)->domain_id);
-
-    return 0;
-}
-
-int mem_sharing_debug_gfn(struct domain *d, unsigned long gfn)
-{
-    p2m_type_t p2mt;
-    mfn_t mfn;
-
-    mfn = get_gfn_query_unlocked(d, gfn, &p2mt);
-
-    gdprintk(XENLOG_DEBUG, "Debug for domain=%d, gfn=%lx, ", 
-               d->domain_id, 
-               gfn);
-    return mem_sharing_debug_mfn(mfn_x(mfn));
-}
-
-#define SHGNT_PER_PAGE_V1 (PAGE_SIZE / sizeof(grant_entry_v1_t))
-#define shared_entry_v1(t, e) \
-    ((t)->shared_v1[(e)/SHGNT_PER_PAGE_V1][(e)%SHGNT_PER_PAGE_V1])
-#define SHGNT_PER_PAGE_V2 (PAGE_SIZE / sizeof(grant_entry_v2_t))
-#define shared_entry_v2(t, e) \
-    ((t)->shared_v2[(e)/SHGNT_PER_PAGE_V2][(e)%SHGNT_PER_PAGE_V2])
-#define STGNT_PER_PAGE (PAGE_SIZE / sizeof(grant_status_t))
-#define status_entry(t, e) \
-    ((t)->status[(e)/STGNT_PER_PAGE][(e)%STGNT_PER_PAGE])
-
-static grant_entry_header_t *
-shared_entry_header(struct grant_table *t, grant_ref_t ref)
-{
-    ASSERT (t->gt_version != 0);
-    if ( t->gt_version == 1 )
-        return (grant_entry_header_t*)&shared_entry_v1(t, ref);
-    else
-        return &shared_entry_v2(t, ref).hdr;
-}
-
-static int mem_sharing_gref_to_gfn(struct domain *d, 
-                                   grant_ref_t ref, 
-                                   unsigned long *gfn)
-{
-    if ( d->grant_table->gt_version < 1 )
-        return -1;
-
-    if ( d->grant_table->gt_version == 1 ) 
-    {
-        grant_entry_v1_t *sha1;
-        sha1 = &shared_entry_v1(d->grant_table, ref);
-        *gfn = sha1->frame;
-    } 
-    else 
-    {
-        grant_entry_v2_t *sha2;
-        sha2 = &shared_entry_v2(d->grant_table, ref);
-        *gfn = sha2->full_page.frame;
-    }
- 
-    return 0;
-}
-
-
-int mem_sharing_debug_gref(struct domain *d, grant_ref_t ref)
-{
-    grant_entry_header_t *shah;
-    uint16_t status;
-    unsigned long gfn;
-
-    if ( d->grant_table->gt_version < 1 )
-    {
-        gdprintk(XENLOG_ERR, 
-                "Asked to debug [dom=%d,gref=%d], but not yet inited.\n",
-                d->domain_id, ref);
-        return -1;
-    }
-    (void)mem_sharing_gref_to_gfn(d, ref, &gfn); 
-    shah = shared_entry_header(d->grant_table, ref);
-    if ( d->grant_table->gt_version == 1 ) 
-        status = shah->flags;
-    else 
-        status = status_entry(d->grant_table, ref);
-    
-    gdprintk(XENLOG_DEBUG,
-            "==> Grant [dom=%d,ref=%d], status=%x. ", 
-            d->domain_id, ref, status);
-
-    return mem_sharing_debug_gfn(d, gfn); 
-}
-
 /* Functions that change a page's type and ownership */
 static int page_make_sharable(struct domain *d, 
                        struct page_info *page, 
@@ -604,6 +499,117 @@ static inline struct page_info *__grab_shared_page(mfn_t mfn)
     return pg;
 }
 
+int mem_sharing_debug_mfn(mfn_t mfn)
+{
+    struct page_info *page;
+    int num_refs;
+
+    if ( (page = __grab_shared_page(mfn)) == NULL)
+    {
+        gdprintk(XENLOG_ERR, "Invalid MFN=%lx\n", mfn_x(mfn));
+        return -1;
+    }
+
+    MEM_SHARING_DEBUG( 
+            "Debug page: MFN=%lx is ci=%lx, ti=%lx, owner_id=%d\n",
+            mfn_x(page_to_mfn(page)), 
+            page->count_info, 
+            page->u.inuse.type_info,
+            page_get_owner(page)->domain_id);
+
+    /* -1 because the page is locked and that's an additional type ref */
+    num_refs = ((int) (page->u.inuse.type_info & PGT_count_mask)) - 1;
+    mem_sharing_page_unlock(page);
+    return num_refs;
+}
+
+int mem_sharing_debug_gfn(struct domain *d, unsigned long gfn)
+{
+    p2m_type_t p2mt;
+    mfn_t mfn;
+    int num_refs;
+
+    mfn = get_gfn_query(d, gfn, &p2mt);
+
+    MEM_SHARING_DEBUG("Debug for domain=%d, gfn=%lx, ", 
+               d->domain_id, 
+               gfn);
+    num_refs = mem_sharing_debug_mfn(mfn);
+    put_gfn(d, gfn);
+    return num_refs;
+}
+
+#define SHGNT_PER_PAGE_V1 (PAGE_SIZE / sizeof(grant_entry_v1_t))
+#define shared_entry_v1(t, e) \
+    ((t)->shared_v1[(e)/SHGNT_PER_PAGE_V1][(e)%SHGNT_PER_PAGE_V1])
+#define SHGNT_PER_PAGE_V2 (PAGE_SIZE / sizeof(grant_entry_v2_t))
+#define shared_entry_v2(t, e) \
+    ((t)->shared_v2[(e)/SHGNT_PER_PAGE_V2][(e)%SHGNT_PER_PAGE_V2])
+#define STGNT_PER_PAGE (PAGE_SIZE / sizeof(grant_status_t))
+#define status_entry(t, e) \
+    ((t)->status[(e)/STGNT_PER_PAGE][(e)%STGNT_PER_PAGE])
+
+static grant_entry_header_t *
+shared_entry_header(struct grant_table *t, grant_ref_t ref)
+{
+    ASSERT (t->gt_version != 0);
+    if ( t->gt_version == 1 )
+        return (grant_entry_header_t*)&shared_entry_v1(t, ref);
+    else
+        return &shared_entry_v2(t, ref).hdr;
+}
+
+static int mem_sharing_gref_to_gfn(struct domain *d, 
+                                   grant_ref_t ref, 
+                                   unsigned long *gfn)
+{
+    if ( d->grant_table->gt_version < 1 )
+        return -1;
+
+    if ( d->grant_table->gt_version == 1 ) 
+    {
+        grant_entry_v1_t *sha1;
+        sha1 = &shared_entry_v1(d->grant_table, ref);
+        *gfn = sha1->frame;
+    } 
+    else 
+    {
+        grant_entry_v2_t *sha2;
+        sha2 = &shared_entry_v2(d->grant_table, ref);
+        *gfn = sha2->full_page.frame;
+    }
+ 
+    return 0;
+}
+
+
+int mem_sharing_debug_gref(struct domain *d, grant_ref_t ref)
+{
+    grant_entry_header_t *shah;
+    uint16_t status;
+    unsigned long gfn;
+
+    if ( d->grant_table->gt_version < 1 )
+    {
+        MEM_SHARING_DEBUG( 
+                "Asked to debug [dom=%d,gref=%d], but not yet inited.\n",
+                d->domain_id, ref);
+        return -1;
+    }
+    (void)mem_sharing_gref_to_gfn(d, ref, &gfn); 
+    shah = shared_entry_header(d->grant_table, ref);
+    if ( d->grant_table->gt_version == 1 ) 
+        status = shah->flags;
+    else 
+        status = status_entry(d->grant_table, ref);
+    
+    MEM_SHARING_DEBUG(
+            "==> Grant [dom=%d,ref=%d], status=%x. ", 
+            d->domain_id, ref, status);
+
+    return mem_sharing_debug_gfn(d, gfn); 
+}
+
 int mem_sharing_nominate_page(struct domain *d,
                               unsigned long gfn,
                               int expected_refcnt,
@@ -1165,7 +1171,7 @@ int mem_sharing_domctl(struct domain *d, xen_domctl_mem_sharing_op_t *mec)
         case XEN_DOMCTL_MEM_EVENT_OP_SHARING_DEBUG_MFN:
         {
             unsigned long mfn = mec->u.debug.u.mfn;
-            rc = mem_sharing_debug_mfn(mfn);
+            rc = mem_sharing_debug_mfn(_mfn(mfn));
         }
         break;