[xen staging] x86/p2m: introduce p2m_is_special()

[patchbot@xxxxxxx]

commit 0bf755e2c856628e11e93c76c3e12974e9964638
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Wed Aug 25 14:17:07 2021 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Aug 25 14:17:07 2021 +0200

    x86/p2m: introduce p2m_is_special()
    
    Seeing the similarity of grant, foreign, and (subsequently) direct-MMIO
    handling, introduce a new P2M type group named "special" (as in "needing
    special accessors to create/destroy").
    
    Also use -EPERM instead of other error codes on the two domain_crash()
    paths touched.
    
    This is part of XSA-378.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Paul Durrant <paul@xxxxxxx>
---
 xen/arch/x86/mm/p2m.c     | 15 +++++++--------
 xen/include/asm-x86/p2m.h |  5 +++++
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index b8bdd55cd2..0ca849ec77 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -817,7 +817,7 @@ p2m_remove_page(struct p2m_domain *p2m, gfn_t gfn, mfn_t 
mfn,
         for ( i = 0; i < (1UL << page_order); i++ )
         {
             p2m->get_entry(p2m, gfn_add(gfn, i), &t, &a, 0, NULL, NULL);
-            if ( !p2m_is_grant(t) && !p2m_is_shared(t) && !p2m_is_foreign(t) )
+            if ( !p2m_is_special(t) && !p2m_is_shared(t) )
                 set_gpfn_from_mfn(mfn_x(mfn) + i, INVALID_M2P_ENTRY);
         }
     }
@@ -954,13 +954,13 @@ guest_physmap_add_entry(struct domain *d, gfn_t gfn, 
mfn_t mfn,
                                   &ot, &a, 0, NULL, NULL);
             ASSERT(!p2m_is_shared(ot));
         }
-        if ( p2m_is_grant(ot) || p2m_is_foreign(ot) )
+        if ( p2m_is_special(ot) )
         {
-            /* Really shouldn't be unmapping grant/foreign maps this way */
+            /* Don't permit unmapping grant/foreign this way. */
             domain_crash(d);
             p2m_unlock(p2m);
             
-            return -EINVAL;
+            return -EPERM;
         }
         else if ( p2m_is_ram(ot) && !p2m_is_paged(ot) )
         {
@@ -1053,8 +1053,7 @@ int p2m_change_type_one(struct domain *d, unsigned long 
gfn_l,
     struct p2m_domain *p2m = p2m_get_hostp2m(d);
     int rc;
 
-    BUG_ON(p2m_is_grant(ot) || p2m_is_grant(nt));
-    BUG_ON(p2m_is_foreign(ot) || p2m_is_foreign(nt));
+    BUG_ON(p2m_is_special(ot) || p2m_is_special(nt));
 
     gfn_lock(p2m, gfn, 0);
 
@@ -1300,11 +1299,11 @@ static int set_typed_p2m_entry(struct domain *d, 
unsigned long gfn_l,
         gfn_unlock(p2m, gfn, order);
         return cur_order + 1;
     }
-    if ( p2m_is_grant(ot) || p2m_is_foreign(ot) )
+    if ( p2m_is_special(ot) )
     {
         gfn_unlock(p2m, gfn, order);
         domain_crash(d);
-        return -ENOENT;
+        return -EPERM;
     }
     else if ( p2m_is_ram(ot) )
     {
diff --git a/xen/include/asm-x86/p2m.h b/xen/include/asm-x86/p2m.h
index b9e35d5e71..bf9967a023 100644
--- a/xen/include/asm-x86/p2m.h
+++ b/xen/include/asm-x86/p2m.h
@@ -154,6 +154,10 @@ typedef unsigned int p2m_query_t;
                             | p2m_to_mask(p2m_ram_logdirty) )
 #define P2M_SHARED_TYPES   (p2m_to_mask(p2m_ram_shared))
 
+/* Types established/cleaned up via special accessors. */
+#define P2M_SPECIAL_TYPES (P2M_GRANT_TYPES | \
+                           p2m_to_mask(p2m_map_foreign))
+
 /* Valid types not necessarily associated with a (valid) MFN. */
 #define P2M_INVALID_MFN_TYPES (P2M_POD_TYPES                  \
                                | p2m_to_mask(p2m_mmio_direct) \
@@ -182,6 +186,7 @@ typedef unsigned int p2m_query_t;
 #define p2m_is_paged(_t)    (p2m_to_mask(_t) & P2M_PAGED_TYPES)
 #define p2m_is_sharable(_t) (p2m_to_mask(_t) & P2M_SHARABLE_TYPES)
 #define p2m_is_shared(_t)   (p2m_to_mask(_t) & P2M_SHARED_TYPES)
+#define p2m_is_special(_t)  (p2m_to_mask(_t) & P2M_SPECIAL_TYPES)
 #define p2m_is_broken(_t)   (p2m_to_mask(_t) & P2M_BROKEN_TYPES)
 #define p2m_is_foreign(_t)  (p2m_to_mask(_t) & p2m_to_mask(p2m_map_foreign))
 
--
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