[PULL 05/10] system/memory: Make ram device region directly accessible

[Peter Xu <peterx@redhat.com>]

From: Gavin Shan <gshan@redhat.com>

This basically reverts 4a2e242bbb30 ("memory: Don't use memcpy for
ram_device regions") to make ram device region directly accessible
again. With this, the bounce buffer is bypassed in address_space_map()
when a ram device region is involved, potentially avoid to overrun
the (small) bounce buffer.

Reported-by: Julia Graham <jugraham@redhat.com>
Suggested-by: Michael S. Tsirkin <mst@redhat.com>
Suggested-by: Peter Xu <peterx@redhat.com>
Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Link: https://lore.kernel.org/r/20260728031731.286666-4-gshan@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 include/system/memory.h | 11 ++---------
 system/memory.c         | 41 +----------------------------------------
 system/trace-events     |  2 --
 3 files changed, 3 insertions(+), 51 deletions(-)

diff --git a/include/system/memory.h b/include/system/memory.h
index 4de5bf2577..1dc761058f 100644
--- a/include/system/memory.h
+++ b/include/system/memory.h
@@ -2718,15 +2718,8 @@ static inline bool memory_region_supports_direct_access(const MemoryRegion *mr)
     if (memory_region_is_romd(mr)) {
         return true;
     }
-    if (!memory_region_is_ram(mr)) {
-        return false;
-    }
-    /*
-     * RAM DEVICE regions can be accessed directly using memcpy, but it might
-     * be MMIO and access using mempy can be wrong (e.g., using instructions not
-     * intended for MMIO access). So we treat this as IO.
-     */
-    return !memory_region_is_ram_device(mr);
+
+    return memory_region_is_ram(mr);
 }
 
 static inline bool memory_access_is_direct(const MemoryRegion *mr,
diff --git a/system/memory.c b/system/memory.c
index 5fc36708ec..da710bbade 100644
--- a/system/memory.c
+++ b/system/memory.c
@@ -1364,43 +1364,6 @@ const MemoryRegionOps unassigned_mem_ops = {
     .endianness = DEVICE_NATIVE_ENDIAN,
 };
 
-static uint64_t memory_region_ram_device_read(void *opaque,
-                                              hwaddr addr, unsigned size)
-{
-    MemoryRegion *mr = opaque;
-    uint64_t data = ldn_he_p(mr->ram_block->host + addr, size);
-
-    trace_memory_region_ram_device_read(get_cpu_index(), mr, addr, data, size);
-
-    return data;
-}
-
-static void memory_region_ram_device_write(void *opaque, hwaddr addr,
-                                           uint64_t data, unsigned size)
-{
-    MemoryRegion *mr = opaque;
-
-    trace_memory_region_ram_device_write(get_cpu_index(), mr, addr, data, size);
-
-    stn_he_p(mr->ram_block->host + addr, size, data);
-}
-
-static const MemoryRegionOps ram_device_mem_ops = {
-    .read = memory_region_ram_device_read,
-    .write = memory_region_ram_device_write,
-    .endianness = HOST_BIG_ENDIAN ? DEVICE_BIG_ENDIAN : DEVICE_LITTLE_ENDIAN,
-    .valid = {
-        .min_access_size = 1,
-        .max_access_size = 8,
-        .unaligned = true,
-    },
-    .impl = {
-        .min_access_size = 1,
-        .max_access_size = 8,
-        .unaligned = true,
-    },
-};
-
 bool memory_region_access_valid(MemoryRegion *mr,
                                 hwaddr addr,
                                 unsigned size,
@@ -1692,10 +1655,8 @@ void memory_region_init_ram_device_ptr(MemoryRegion *mr, Object *owner,
                                        const char *name, uint64_t size,
                                        void *ptr)
 {
-    memory_region_init_io(mr, owner, &ram_device_mem_ops, mr, name, size);
-    mr->ram = true;
+    memory_region_init_ram_ptr(mr, owner, name, size, ptr);
     mr->ram_device = true;
-    memory_region_set_ram_ptr(mr, size, ptr);
 }
 
 void memory_region_init_alias(MemoryRegion *mr, Object *owner,
diff --git a/system/trace-events b/system/trace-events
index 51b4a4679a..d483b31419 100644
--- a/system/trace-events
+++ b/system/trace-events
@@ -20,8 +20,6 @@ memory_region_ops_read(int cpu_index, void *mr, uint64_t addr, uint64_t value, u
 memory_region_ops_write(int cpu_index, void *mr, uint64_t addr, uint64_t value, unsigned size, const char *name) "cpu %d mr %p addr 0x%"PRIx64" value 0x%"PRIx64" size %u name '%s'"
 memory_region_subpage_read(int cpu_index, void *mr, uint64_t offset, uint64_t value, unsigned size) "cpu %d mr %p offset 0x%"PRIx64" value 0x%"PRIx64" size %u"
 memory_region_subpage_write(int cpu_index, void *mr, uint64_t offset, uint64_t value, unsigned size) "cpu %d mr %p offset 0x%"PRIx64" value 0x%"PRIx64" size %u"
-memory_region_ram_device_read(int cpu_index, void *mr, uint64_t addr, uint64_t value, unsigned size) "cpu %d mr %p addr 0x%"PRIx64" value 0x%"PRIx64" size %u"
-memory_region_ram_device_write(int cpu_index, void *mr, uint64_t addr, uint64_t value, unsigned size) "cpu %d mr %p addr 0x%"PRIx64" value 0x%"PRIx64" size %u"
 memory_region_sync_dirty(const char *mr, const char *listener, int global) "mr '%s' listener '%s' synced (global=%d)"
 flatview_new(void *view, void *root) "%p (root %p)"
 flatview_destroy(void *view, void *root) "%p (root %p)"
-- 
2.54.0