[Qemu-devel] [PATCH v6 39/47] qemu_ram_block_from_host

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Postcopy sends RAMBlock names and offsets over the wire (since it can't
rely on the order of ramaddr being the same), and it starts out with
HVA fault addresses from the kernel.

qemu_ram_block_from_host translates a HVA into a RAMBlock, an offset
in the RAMBlock and the global ram_addr_t value.

Rewrite qemu_ram_addr_from_host to use qemu_ram_block_from_host.

Provide qemu_ram_get_idstr since its the actual name text sent on the
wire.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
---
 exec.c                    | 54 +++++++++++++++++++++++++++++++++++++++--------
 include/exec/cpu-common.h |  3 +++
 2 files changed, 48 insertions(+), 9 deletions(-)

diff --git a/exec.c b/exec.c
index c3027cf..86f2b87 100644
--- a/exec.c
+++ b/exec.c
@@ -1280,6 +1280,11 @@ static RAMBlock *find_ram_block(ram_addr_t addr)
     return NULL;
 }
 
+const char *qemu_ram_get_idstr(RAMBlock *rb)
+{
+    return rb->idstr;
+}
+
 /* Called with iothread lock held.  */
 void qemu_ram_set_idstr(ram_addr_t addr, const char *name, DeviceState *dev)
 {
@@ -1768,8 +1773,16 @@ static void *qemu_ram_ptr_length(ram_addr_t addr, hwaddr *size)
     }
 }
 
-/* Some of the softmmu routines need to translate from a host pointer
- * (typically a TLB entry) back to a ram offset.
+/*
+ * Translates a host ptr back to a RAMBlock, a ram_addr and an offset
+ * in that RAMBlock.
+ *
+ * ptr: Host pointer to look up
+ * round_offset: If true round the result offset down to a page boundary
+ * *ram_addr: set to result ram_addr
+ * *offset: set to result offset within the RAMBlock
+ *
+ * Returns: RAMBlock (or NULL if not found)
  *
  * By the time this function returns, the returned pointer is not protected
  * by RCU anymore.  If the caller is not within an RCU critical section and
@@ -1777,18 +1790,22 @@ static void *qemu_ram_ptr_length(ram_addr_t addr, hwaddr *size)
  * pointer, such as a reference to the region that includes the incoming
  * ram_addr_t.
  */
-MemoryRegion *qemu_ram_addr_from_host(void *ptr, ram_addr_t *ram_addr)
+RAMBlock *qemu_ram_block_from_host(void *ptr, bool round_offset,
+                                   ram_addr_t *ram_addr,
+                                   ram_addr_t *offset)
 {
     RAMBlock *block;
     uint8_t *host = ptr;
-    MemoryRegion *mr;
 
     if (xen_enabled()) {
         rcu_read_lock();
         *ram_addr = xen_ram_addr_from_mapcache(ptr);
-        mr = qemu_get_ram_block(*ram_addr)->mr;
+        block = qemu_get_ram_block(*ram_addr);
+        if (block) {
+            *offset = (host - block->host);
+        }
         rcu_read_unlock();
-        return mr;
+        return block;
     }
 
     rcu_read_lock();
@@ -1811,10 +1828,29 @@ MemoryRegion *qemu_ram_addr_from_host(void *ptr, ram_addr_t *ram_addr)
     return NULL;
 
 found:
-    *ram_addr = block->offset + (host - block->host);
-    mr = block->mr;
+    *offset = (host - block->host);
+    if (round_offset) {
+        *offset &= TARGET_PAGE_MASK;
+    }
+    *ram_addr = block->offset + *offset;
     rcu_read_unlock();
-    return mr;
+    return block;
+}
+
+/* Some of the softmmu routines need to translate from a host pointer
+   (typically a TLB entry) back to a ram offset.  */
+MemoryRegion *qemu_ram_addr_from_host(void *ptr, ram_addr_t *ram_addr)
+{
+    RAMBlock *block;
+    ram_addr_t offset; /* Not used */
+
+    block = qemu_ram_block_from_host(ptr, false, ram_addr, &offset);
+
+    if (!block) {
+        return NULL;
+    }
+
+    return block->mr;
 }
 
 static void notdirty_mem_write(void *opaque, hwaddr ram_addr,
diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
index 2abecac..13f8d3a 100644
--- a/include/exec/cpu-common.h
+++ b/include/exec/cpu-common.h
@@ -62,8 +62,11 @@ typedef uint32_t CPUReadMemoryFunc(void *opaque, hwaddr addr);
 void qemu_ram_remap(ram_addr_t addr, ram_addr_t length);
 /* This should not be used by devices.  */
 MemoryRegion *qemu_ram_addr_from_host(void *ptr, ram_addr_t *ram_addr);
+RAMBlock *qemu_ram_block_from_host(void *ptr, bool round_offset,
+                                   ram_addr_t *ram_addr, ram_addr_t *offset);
 void qemu_ram_set_idstr(ram_addr_t addr, const char *name, DeviceState *dev);
 void qemu_ram_unset_idstr(ram_addr_t addr);
+const char *qemu_ram_get_idstr(RAMBlock *rb);
 
 void cpu_physical_memory_rw(hwaddr addr, uint8_t *buf,
                             int len, int is_write);
-- 
2.1.0