Subject: xenpaging: page-in granttable entries

When converting a gfn to mfn, check if the page is paged-out.
If it is, request a page-in and return GNTST_eagain to the caller
to indicate a retry of the hypercall is required.
This fixes granttable errors when xenpaging is enabled in the guest.

(xen-unstable changeset:   22209:50c1cc209f8f)

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Already-Acked-by: Patrick Colp <pjcolp@cs.ubc.ca>
Already-Acked-by: Keir Fraser <keir.fraser@citrix.com>

---
 xen/common/grant_table.c |   94 ++++++++++++++++++++++++++++++-----------------
 1 file changed, 60 insertions(+), 34 deletions(-)

Index: xen-4.0.2-testing/xen/common/grant_table.c
===================================================================
--- xen-4.0.2-testing.orig/xen/common/grant_table.c
+++ xen-4.0.2-testing/xen/common/grant_table.c
@@ -139,6 +139,37 @@ shared_entry_header(struct grant_table *
 #define active_entry(t, e) \
     ((t)->active[(e)/ACGNT_PER_PAGE][(e)%ACGNT_PER_PAGE])
 
+/* Check if the page has been paged out */
+static int __get_paged_frame(unsigned long gfn, unsigned long *frame, int readonly, struct domain *rd)
+{
+    p2m_type_t p2mt;
+    mfn_t mfn;
+    int rc = GNTST_okay;
+
+    if ( readonly )
+        mfn = gfn_to_mfn(rd, gfn, &p2mt);
+    else
+        mfn = gfn_to_mfn_unshare(rd, gfn, &p2mt, 1);
+
+    if ( p2m_is_valid(p2mt) )
+    {
+        *frame = mfn_x(mfn);
+        if ( p2m_is_paging(p2mt) )
+        {
+            if ( p2m_is_paged(p2mt) )
+                p2m_mem_paging_populate(rd, gfn);
+            rc = GNTST_eagain;
+        }
+    }
+    else
+    {
+        *frame = INVALID_MFN;
+        rc = GNTST_bad_page;
+    }
+
+    return rc;
+}
+
 static inline int
 __get_maptrack_handle(
     struct grant_table *t)
@@ -527,14 +558,16 @@ __gnttab_map_grant_ref(
 
         if ( !act->pin )
         {
+            unsigned long gfn;
+            unsigned long frame;
+
+            gfn = sha1 ? sha1->frame : sha2->full_page.frame;
+            rc = __get_paged_frame(gfn, &frame, !!(op->flags & GNTMAP_readonly), rd);
+            if ( rc != GNTST_okay )
+                goto unlock_out;
+            act->gfn = gfn;
             act->domid = ld->domain_id;
-            if ( sha1 )
-                act->gfn = sha1->frame;
-            else
-                act->gfn = sha2->full_page.frame;
-            act->frame = (op->flags & GNTMAP_readonly) ?  
-                            gmfn_to_mfn(rd, act->gfn) :
-                            gfn_to_mfn_private(rd, act->gfn); 
+            act->frame = frame;
             act->start = 0;
             act->length = PAGE_SIZE;
             act->is_sub_page = 0;
@@ -1697,6 +1730,7 @@ __acquire_grant_for_copy(
     domid_t trans_domid;
     grant_ref_t trans_gref;
     struct domain *rrd;
+    unsigned long gfn;
     unsigned long grant_frame;
     unsigned trans_page_off;
     unsigned trans_length;
@@ -1814,9 +1848,11 @@ __acquire_grant_for_copy(
         }
         else if ( sha1 )
         {
-            act->gfn = sha1->frame;
-            grant_frame = readonly ? gmfn_to_mfn(rd, act->gfn) :
-                                     gfn_to_mfn_private(rd, act->gfn);
+            gfn = sha1->frame;
+            rc = __get_paged_frame(gfn, &grant_frame, readonly, rd);
+            if ( rc != GNTST_okay )
+                goto unlock_out;
+            act->gfn = gfn;
             is_sub_page = 0;
             trans_page_off = 0;
             trans_length = PAGE_SIZE;
@@ -1824,9 +1860,11 @@ __acquire_grant_for_copy(
         }
         else if ( !(sha2->hdr.flags & GTF_sub_page) )
         {
-            act->gfn = sha2->full_page.frame;
-            grant_frame = readonly ? gmfn_to_mfn(rd, act->gfn) :
-                                     gfn_to_mfn_private(rd, act->gfn);
+            gfn = sha2->full_page.frame;
+            rc = __get_paged_frame(gfn, &grant_frame, readonly, rd);
+            if ( rc != GNTST_okay )
+                goto unlock_out;
+            act->gfn = gfn;
             is_sub_page = 0;
             trans_page_off = 0;
             trans_length = PAGE_SIZE;
@@ -1834,9 +1872,11 @@ __acquire_grant_for_copy(
         }
         else
         {
-            act->gfn = sha2->sub_page.frame;
-            grant_frame = readonly ? gmfn_to_mfn(rd, act->gfn) :
-                                     gfn_to_mfn_private(rd, act->gfn);
+            gfn = sha2->sub_page.frame;
+            rc = __get_paged_frame(gfn, &grant_frame, readonly, rd);
+            if ( rc != GNTST_okay )
+                goto unlock_out;
+            act->gfn = gfn;
             is_sub_page = 1;
             trans_page_off = sha2->sub_page.page_off;
             trans_length = sha2->sub_page.length;
@@ -1932,16 +1972,9 @@ __gnttab_copy(
     else
     {
 #ifdef CONFIG_X86
-        p2m_type_t p2mt;
-        s_frame = mfn_x(gfn_to_mfn(sd, op->source.u.gmfn, &p2mt));
-        if ( !p2m_is_valid(p2mt) )
-          s_frame = INVALID_MFN;
-        if ( p2m_is_paging(p2mt) )
-        {
-            p2m_mem_paging_populate(sd, op->source.u.gmfn);
-            rc = -ENOENT;
+        rc = __get_paged_frame(op->source.u.gmfn, &s_frame, 1, sd);
+        if ( rc != GNTST_okay )
             goto error_out;
-        }
 #else
         s_frame = gmfn_to_mfn(sd, op->source.u.gmfn);        
 #endif
@@ -1978,16 +2011,9 @@ __gnttab_copy(
     else
     {
 #ifdef CONFIG_X86
-        p2m_type_t p2mt;
-        d_frame = mfn_x(gfn_to_mfn_unshare(dd, op->dest.u.gmfn, &p2mt, 1));
-        if ( !p2m_is_valid(p2mt) )
-          d_frame = INVALID_MFN;
-        if ( p2m_is_paging(p2mt) )
-        {
-            p2m_mem_paging_populate(dd, op->dest.u.gmfn);
-            rc = -ENOENT;
+        rc = __get_paged_frame(op->dest.u.gmfn, &d_frame, 0, dd);
+        if ( rc != GNTST_okay )
             goto error_out;
-        }
 #else
         d_frame = gmfn_to_mfn(dd, op->dest.u.gmfn);
 #endif