Re: [Xen-ia64-devel] [PATCH] fix XENMEM_add_to_physmap with XENMAPSPACE_mfn

[Isaku Yamahata <yamahata@xxxxxxxxxxxxx>]

The previous patch was wrong. Here is the updated one.

[IA64] fix XENMEM_add_to_physmap with XENMAPSPACE_mfn

In case of XENMEM_add_to_physmap with XENMAPSPACE_mfn,
it triggers BUG_ON(). In fact it breaks some assumptions.
Update BUG_ON() conditions.

Signed-off-by: Isaku Yamahata <yamahata@xxxxxxxxxxxxx>

diff -r d0a544d8a3f3 xen/arch/ia64/xen/mm.c
--- a/xen/arch/ia64/xen/mm.c    Mon Sep 01 16:59:43 2008 +0900
+++ b/xen/arch/ia64/xen/mm.c    Fri Sep 12 14:32:44 2008 +0900
@@ -1227,7 +1227,7 @@
 adjust_page_count_info(struct page_info* page)
 {
     struct domain* d = page_get_owner(page);
-    BUG_ON((page->count_info & PGC_count_mask) != 1);
+    BUG_ON((page->count_info & PGC_count_mask) < 1);
     if (d != NULL) {
         int ret = get_page(page, d);
         BUG_ON(ret == 0);
@@ -1272,6 +1272,7 @@
             //
             // guest_remove_page(): owner = d, count_info = 1
             // memory_exchange(): owner = NULL, count_info = 1
+            // XENMEM_add_to_physmap: ower = d, count_info >= 1
             adjust_page_count_info(page);
         }
     }
@@ -2422,6 +2423,16 @@
     return 0;
 }
 
+static void
+__guest_physmap_add_page(struct domain *d, unsigned long gpfn,
+                         unsigned long mfn)
+{
+    set_gpfn_from_mfn(mfn, gpfn);
+    smp_mb();
+    assign_domain_page_replace(d, gpfn << PAGE_SHIFT, mfn,
+                               ASSIGN_writable | ASSIGN_pgc_allocated);
+}
+
 int
 guest_physmap_add_page(struct domain *d, unsigned long gpfn,
                        unsigned long mfn, unsigned int page_order)
@@ -2431,10 +2442,7 @@
     for (i = 0; i < (1UL << page_order); i++) {
         BUG_ON(!mfn_valid(mfn));
         BUG_ON(mfn_to_page(mfn)->count_info != (PGC_allocated | 1));
-        set_gpfn_from_mfn(mfn, gpfn);
-        smp_mb();
-        assign_domain_page_replace(d, gpfn << PAGE_SHIFT, mfn,
-                                   ASSIGN_writable | ASSIGN_pgc_allocated);
+        __guest_physmap_add_page(d, gpfn, mfn);
         mfn++;
         gpfn++;
     }
@@ -2894,7 +2902,9 @@
             guest_physmap_remove_page(d, gpfn, mfn, 0);
 
         /* Map at new location. */
-        guest_physmap_add_page(d, xatp.gpfn, mfn, 0);
+        /* Here page->count_info = PGC_allocated | N where N >= 1*/
+        __guest_physmap_add_page(d, xatp.gpfn, mfn);
+        page = NULL; /* prevent put_page() */
 
     out:
         domain_unlock(d);


-- 
yamahata

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