xen: mapcache: Split mapcache_grants by ro and rw

Today, we don't track write-abiliy in the cache, if a user
requests a readable mapping followed by a writeable mapping
on the same page, the second lookup will incorrectly hit
the readable entry.

Split mapcache_grants by ro and rw access. Grants will now
have separate ways in the cache depending on writeability.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@amd.com>
(cherry picked from commit 88fb705600a3b612c571efc9f1a6aed923a18dcc)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

hw/xen/xen-mapcache.c

@@ -75,7 +75,8 @@ typedef struct MapCache {
 } MapCache;
 
 static MapCache *mapcache;
-static MapCache *mapcache_grants;
+static MapCache *mapcache_grants_ro;
+static MapCache *mapcache_grants_rw;
 static xengnttab_handle *xen_region_gnttabdev;
 
 static inline void mapcache_lock(MapCache *mc)
@@ -176,9 +177,12 @@ void xen_map_cache_init(phys_offset_to_gaddr_t f, void *opaque)
      * Grant mappings must use XC_PAGE_SIZE granularity since we can't
      * map anything beyond the number of pages granted to us.
      */
-    mapcache_grants = xen_map_cache_init_single(f, opaque,
-                                                XC_PAGE_SHIFT,
-                                                max_mcache_size);
+    mapcache_grants_ro = xen_map_cache_init_single(f, opaque,
+                                                   XC_PAGE_SHIFT,
+                                                   max_mcache_size);
+    mapcache_grants_rw = xen_map_cache_init_single(f, opaque,
+                                                   XC_PAGE_SHIFT,
+                                                   max_mcache_size);
 
     setrlimit(RLIMIT_AS, &rlimit_as);
 }
@@ -456,9 +460,13 @@ uint8_t *xen_map_cache(MemoryRegion *mr,
                        bool is_write)
 {
     bool grant = xen_mr_is_grants(mr);
-    MapCache *mc = grant ? mapcache_grants : mapcache;
+    MapCache *mc = mapcache;
     uint8_t *p;
 
+    if (grant) {
+        mc = is_write ? mapcache_grants_rw : mapcache_grants_ro;
+    }
+
     if (grant && !lock) {
         /*
          * Grants are only supported via address_space_map(). Anything
@@ -523,7 +531,10 @@ ram_addr_t xen_ram_addr_from_mapcache(void *ptr)
 
     addr = xen_ram_addr_from_mapcache_single(mapcache, ptr);
     if (addr == RAM_ADDR_INVALID) {
-        addr = xen_ram_addr_from_mapcache_single(mapcache_grants, ptr);
+        addr = xen_ram_addr_from_mapcache_single(mapcache_grants_ro, ptr);
+    }
+    if (addr == RAM_ADDR_INVALID) {
+        addr = xen_ram_addr_from_mapcache_single(mapcache_grants_rw, ptr);
     }
 
     return addr;
@@ -626,7 +637,8 @@ static void xen_invalidate_map_cache_entry_single(MapCache *mc, uint8_t *buffer)
 static void xen_invalidate_map_cache_entry_all(uint8_t *buffer)
 {
     xen_invalidate_map_cache_entry_single(mapcache, buffer);
-    xen_invalidate_map_cache_entry_single(mapcache_grants, buffer);
+    xen_invalidate_map_cache_entry_single(mapcache_grants_ro, buffer);
+    xen_invalidate_map_cache_entry_single(mapcache_grants_rw, buffer);
 }
 
 static void xen_invalidate_map_cache_entry_bh(void *opaque)