exec: reintroduce MemoryRegion caching

MemoryRegionCache was reverted to "normal" address_space_* operations
for 2.9, due to lack of support for IOMMUs.  Reinstate the
optimizations, caching only the IOMMU translation at address_cache_init
but not the IOMMU lookup and target AddressSpace translation are not
cached; now that MemoryRegionCache supports IOMMUs, it becomes more widely
applicable too.

The inlined fast path is defined in memory_ldst_cached.inc.h, while the
slow path uses memory_ldst.inc.c as before.  The smaller fast path causes
a little code size reduction in MemoryRegionCache users:

    hw/virtio/virtio.o text size before: 32373
    hw/virtio/virtio.o text size after: 31941

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

include/exec/cpu-all.h

@@ -175,7 +175,7 @@ extern unsigned long reserved_va;
 #define TARGET_ENDIANNESS
 #include "exec/memory_ldst.inc.h"
 
-#define SUFFIX       _cached
+#define SUFFIX       _cached_slow
 #define ARG1         cache
 #define ARG1_DECL    MemoryRegionCache *cache
 #define TARGET_ENDIANNESS
@@ -193,6 +193,10 @@ static inline void stl_phys_notdirty(AddressSpace *as, hwaddr addr, uint32_t val
 #define TARGET_ENDIANNESS
 #include "exec/memory_ldst_phys.inc.h"
 
+/* Inline fast path for direct RAM access.  */
+#define ENDIANNESS
+#include "exec/memory_ldst_cached.inc.h"
+
 #define SUFFIX       _cached
 #define ARG1         cache
 #define ARG1_DECL    MemoryRegionCache *cache

include/exec/memory-internal.h

@@ -31,6 +31,9 @@ static inline AddressSpaceDispatch *address_space_to_dispatch(AddressSpace *as)
     return flatview_to_dispatch(address_space_to_flatview(as));
 }
 
+FlatView *address_space_get_flatview(AddressSpace *as);
+void flatview_unref(FlatView *view);
+
 extern const MemoryRegionOps unassigned_mem_ops;
 
 bool memory_region_access_valid(MemoryRegion *mr, hwaddr addr,

include/exec/memory.h

@@ -1688,12 +1688,16 @@ MemTxResult address_space_write(AddressSpace *as, hwaddr addr,
 #include "exec/memory_ldst_phys.inc.h"
 
 struct MemoryRegionCache {
+    void *ptr;
     hwaddr xlat;
     hwaddr len;
-    AddressSpace *as;
+    FlatView *fv;
+    MemoryRegionSection mrs;
+    bool is_write;
 };
 
-#define MEMORY_REGION_CACHE_INVALID ((MemoryRegionCache) { .as = NULL })
+#define MEMORY_REGION_CACHE_INVALID ((MemoryRegionCache) { .mrs.mr = NULL })
+
 
 /* address_space_ld*_cached: load from a cached #MemoryRegion
  * address_space_st*_cached: store into a cached #MemoryRegion
@@ -1719,11 +1723,40 @@ struct MemoryRegionCache {
  *   if NULL, this information is discarded
  */
 
-#define SUFFIX       _cached
+#define SUFFIX       _cached_slow
 #define ARG1         cache
 #define ARG1_DECL    MemoryRegionCache *cache
 #include "exec/memory_ldst.inc.h"
 
+/* Inline fast path for direct RAM access.  */
+static inline uint8_t address_space_ldub_cached(MemoryRegionCache *cache,
+    hwaddr addr, MemTxAttrs attrs, MemTxResult *result)
+{
+    assert(addr < cache->len);
+    if (likely(cache->ptr)) {
+        return ldub_p(cache->ptr + addr);
+    } else {
+        return address_space_ldub_cached_slow(cache, addr, attrs, result);
+    }
+}
+
+static inline void address_space_stb_cached(MemoryRegionCache *cache,
+    hwaddr addr, uint32_t val, MemTxAttrs attrs, MemTxResult *result)
+{
+    assert(addr < cache->len);
+    if (likely(cache->ptr)) {
+        stb_p(cache->ptr + addr, val);
+    } else {
+        address_space_stb_cached_slow(cache, addr, val, attrs, result);
+    }
+}
+
+#define ENDIANNESS   _le
+#include "exec/memory_ldst_cached.inc.h"
+
+#define ENDIANNESS   _be
+#include "exec/memory_ldst_cached.inc.h"
+
 #define SUFFIX       _cached
 #define ARG1         cache
 #define ARG1_DECL    MemoryRegionCache *cache
@@ -1860,6 +1893,13 @@ MemTxResult flatview_read_continue(FlatView *fv, hwaddr addr,
                                    MemoryRegion *mr);
 void *qemu_map_ram_ptr(RAMBlock *ram_block, ram_addr_t addr);
 
+/* Internal functions, part of the implementation of address_space_read_cached
+ * and address_space_write_cached.  */
+void address_space_read_cached_slow(MemoryRegionCache *cache,
+                                    hwaddr addr, void *buf, int len);
+void address_space_write_cached_slow(MemoryRegionCache *cache,
+                                     hwaddr addr, const void *buf, int len);
+
 static inline bool memory_access_is_direct(MemoryRegion *mr, bool is_write)
 {
     if (is_write) {
@@ -1928,7 +1968,11 @@ address_space_read_cached(MemoryRegionCache *cache, hwaddr addr,
                           void *buf, int len)
 {
     assert(addr < cache->len && len <= cache->len - addr);
-    address_space_read(cache->as, cache->xlat + addr, MEMTXATTRS_UNSPECIFIED, buf, len);
+    if (likely(cache->ptr)) {
+        memcpy(buf, cache->ptr + addr, len);
+    } else {
+        address_space_read_cached_slow(cache, addr, buf, len);
+    }
 }
 
 /**
@@ -1944,7 +1988,11 @@ address_space_write_cached(MemoryRegionCache *cache, hwaddr addr,
                            void *buf, int len)
 {
     assert(addr < cache->len && len <= cache->len - addr);
-    address_space_write(cache->as, cache->xlat + addr, MEMTXATTRS_UNSPECIFIED, buf, len);
+    if (likely(cache->ptr)) {
+        memcpy(cache->ptr + addr, buf, len);
+    } else {
+        address_space_write_cached_slow(cache, addr, buf, len);
+    }
 }
 
 #endif

include/exec/memory_ldst_cached.inc.h

@@ -0,0 +1,108 @@
+/*
+ *  Memory access templates for MemoryRegionCache
+ *
+ *  Copyright (c) 2018 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#define ADDRESS_SPACE_LD_CACHED(size) \
+    glue(glue(address_space_ld, size), glue(ENDIANNESS, _cached))
+#define ADDRESS_SPACE_LD_CACHED_SLOW(size) \
+    glue(glue(address_space_ld, size), glue(ENDIANNESS, _cached_slow))
+#define LD_P(size) \
+    glue(glue(ld, size), glue(ENDIANNESS, _p))
+
+static inline uint32_t ADDRESS_SPACE_LD_CACHED(l)(MemoryRegionCache *cache,
+    hwaddr addr, MemTxAttrs attrs, MemTxResult *result)
+{
+    assert(addr < cache->len && 4 <= cache->len - addr);
+    if (likely(cache->ptr)) {
+        return LD_P(l)(cache->ptr + addr);
+    } else {
+        return ADDRESS_SPACE_LD_CACHED_SLOW(l)(cache, addr, attrs, result);
+    }
+}
+
+static inline uint64_t ADDRESS_SPACE_LD_CACHED(q)(MemoryRegionCache *cache,
+    hwaddr addr, MemTxAttrs attrs, MemTxResult *result)
+{
+    assert(addr < cache->len && 8 <= cache->len - addr);
+    if (likely(cache->ptr)) {
+        return LD_P(q)(cache->ptr + addr);
+    } else {
+        return ADDRESS_SPACE_LD_CACHED_SLOW(q)(cache, addr, attrs, result);
+    }
+}
+
+static inline uint32_t ADDRESS_SPACE_LD_CACHED(uw)(MemoryRegionCache *cache,
+    hwaddr addr, MemTxAttrs attrs, MemTxResult *result)
+{
+    assert(addr < cache->len && 2 <= cache->len - addr);
+    if (likely(cache->ptr)) {
+        return LD_P(uw)(cache->ptr + addr);
+    } else {
+        return ADDRESS_SPACE_LD_CACHED_SLOW(uw)(cache, addr, attrs, result);
+    }
+}
+
+#undef ADDRESS_SPACE_LD_CACHED
+#undef ADDRESS_SPACE_LD_CACHED_SLOW
+#undef LD_P
+
+#define ADDRESS_SPACE_ST_CACHED(size) \
+    glue(glue(address_space_st, size), glue(ENDIANNESS, _cached))
+#define ADDRESS_SPACE_ST_CACHED_SLOW(size) \
+    glue(glue(address_space_st, size), glue(ENDIANNESS, _cached_slow))
+#define ST_P(size) \
+    glue(glue(st, size), glue(ENDIANNESS, _p))
+
+static inline void ADDRESS_SPACE_ST_CACHED(l)(MemoryRegionCache *cache,
+    hwaddr addr, uint32_t val, MemTxAttrs attrs, MemTxResult *result)
+{
+    assert(addr < cache->len && 4 <= cache->len - addr);
+    if (likely(cache->ptr)) {
+        ST_P(l)(cache->ptr + addr, val);
+    } else {
+        ADDRESS_SPACE_ST_CACHED_SLOW(l)(cache, addr, val, attrs, result);
+    }
+}
+
+static inline void ADDRESS_SPACE_ST_CACHED(w)(MemoryRegionCache *cache,
+    hwaddr addr, uint32_t val, MemTxAttrs attrs, MemTxResult *result)
+{
+    assert(addr < cache->len && 2 <= cache->len - addr);
+    if (likely(cache->ptr)) {
+        ST_P(w)(cache->ptr + addr, val);
+    } else {
+        ADDRESS_SPACE_ST_CACHED_SLOW(w)(cache, addr, val, attrs, result);
+    }
+}
+
+static inline void ADDRESS_SPACE_ST_CACHED(q)(MemoryRegionCache *cache,
+    hwaddr addr, uint64_t val, MemTxAttrs attrs, MemTxResult *result)
+{
+    assert(addr < cache->len && 8 <= cache->len - addr);
+    if (likely(cache->ptr)) {
+        ST_P(q)(cache->ptr + addr, val);
+    } else {
+        ADDRESS_SPACE_ST_CACHED_SLOW(q)(cache, addr, val, attrs, result);
+    }
+}
+
+#undef ADDRESS_SPACE_ST_CACHED
+#undef ADDRESS_SPACE_ST_CACHED_SLOW
+#undef ST_P
+
+#undef ENDIANNESS