qemu_ram_block_host_offset

Utility to give the offset of a host pointer within a RAMBlock
(assuming we already know it's in that RAMBlock)

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

exec.c

@@ -2297,6 +2297,16 @@ static void *qemu_ram_ptr_length(RAMBlock *ram_block, ram_addr_t addr,
     return ramblock_ptr(block, addr);
 }
 
+/* Return the offset of a hostpointer within a ramblock */
+ram_addr_t qemu_ram_block_host_offset(RAMBlock *rb, void *host)
+{
+    ram_addr_t res = (uint8_t *)host - (uint8_t *)rb->host;
+    assert((uintptr_t)host >= (uintptr_t)rb->host);
+    assert(res < rb->max_length);
+
+    return res;
+}
+
 /*
  * Translates a host ptr back to a RAMBlock, a ram_addr and an offset
  * in that RAMBlock.

include/exec/cpu-common.h

@@ -68,6 +68,7 @@ ram_addr_t qemu_ram_addr_from_host(void *ptr);
 RAMBlock *qemu_ram_block_by_name(const char *name);
 RAMBlock *qemu_ram_block_from_host(void *ptr, bool round_offset,
                                    ram_addr_t *offset);
+ram_addr_t qemu_ram_block_host_offset(RAMBlock *rb, void *host);
 void qemu_ram_set_idstr(RAMBlock *block, const char *name, DeviceState *dev);
 void qemu_ram_unset_idstr(RAMBlock *block);
 const char *qemu_ram_get_idstr(RAMBlock *rb);