x86/mm/p2m: merge gfn_to_mfn_unshare with other gfn_to_mfn paths.

gfn_to_mfn_unshare() had its own function despite all other lookup types
being handled in one place. Merge it into _gfn_to_mfn_type(), so that it
gets the benefit of broken-page protection, for example, and tidy its
interfaces up to fit.

The unsharing code still has a lot of bugs, e.g.
 - failure to alloc for unshare on a foreign lookup still BUG()s,
 - at least one race condition in unshare-and-retry
 - p2m_* lookup types should probably be flags, not enum
but it's cleaner and will make later p2m cleanups easier.

Signed-off-by: Tim Deegan <Tim.Deegan@citrix.com>

1 files changed, 8 insertions, 2 deletions

diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c
index e3ad8e60c2..ba32a358a5 100644
--- a/xen/common/grant_table.c
+++ b/xen/common/grant_table.c
@@ -110,7 +110,8 @@ static unsigned inline int max_nr_maptrack_frames(void)
 #define gfn_to_mfn_private(_d, _gfn) ({                     \
     p2m_type_t __p2mt;                                      \
     unsigned long __x;                                      \
-    __x = mfn_x(gfn_to_mfn_unshare(p2m_get_hostp2m(_d), _gfn, &__p2mt, 1));  \
+    __x = mfn_x(gfn_to_mfn_unshare(p2m_get_hostp2m(_d), _gfn, &__p2mt));  \
+    BUG_ON(p2m_is_shared(__p2mt)); /* XXX fixme */          \
     if ( !p2m_is_valid(__p2mt) )                            \
         __x = INVALID_MFN;                                  \
     __x; })
@@ -153,7 +154,12 @@ static int __get_paged_frame(unsigned long gfn, unsigned long *frame, int readon
     if ( readonly )
         mfn = gfn_to_mfn(p2m, gfn, &p2mt);
     else
-        mfn = gfn_to_mfn_unshare(p2m, gfn, &p2mt, 1);
+    {
+        mfn = gfn_to_mfn_unshare(p2m, gfn, &p2mt);
+        BUG_ON(p2m_is_shared(p2mt));
+        /* XXX Here, and above in gfn_to_mfn_private, need to handle
+         * XXX failure to unshare. */
+    }
 
     if ( p2m_is_valid(p2mt) ) {
         *frame = mfn_x(mfn);