[PATCH v3 02/18] system/memory: Better describe @plen argument of flatview_translate()

[Philippe Mathieu-Daudé <philmd@xxxxxxxxxx>]

flatview_translate()'s @plen argument is output-only and can be NULL.

When Xen is enabled, only update @plen_out when non-NULL.

Signed-off-by: Philippe Mathieu-Daudé <philmd@xxxxxxxxxx>
---
 include/system/memory.h | 5 +++--
 system/physmem.c        | 9 +++++----
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/include/system/memory.h b/include/system/memory.h
index aa85fc27a10..3e5bf3ef05e 100644
--- a/include/system/memory.h
+++ b/include/system/memory.h
@@ -2992,13 +2992,14 @@ IOMMUTLBEntry 
address_space_get_iotlb_entry(AddressSpace *as, hwaddr addr,
  * @addr: address within that address space
  * @xlat: pointer to address within the returned memory region section's
  * #MemoryRegion.
- * @len: pointer to length
+ * @plen_out: pointer to valid read/write length of the translated address.
+ *            It can be @NULL when we don't care about it.
  * @is_write: indicates the transfer direction
  * @attrs: memory attributes
  */
 MemoryRegion *flatview_translate(FlatView *fv,
                                  hwaddr addr, hwaddr *xlat,
-                                 hwaddr *len, bool is_write,
+                                 hwaddr *plen_out, bool is_write,
                                  MemTxAttrs attrs);
 
 static inline MemoryRegion *address_space_translate(AddressSpace *as,
diff --git a/system/physmem.c b/system/physmem.c
index 8a8be3a80e2..86422f294e2 100644
--- a/system/physmem.c
+++ b/system/physmem.c
@@ -566,7 +566,7 @@ iotlb_fail:
 
 /* Called from RCU critical section */
 MemoryRegion *flatview_translate(FlatView *fv, hwaddr addr, hwaddr *xlat,
-                                 hwaddr *plen, bool is_write,
+                                 hwaddr *plen_out, bool is_write,
                                  MemTxAttrs attrs)
 {
     MemoryRegion *mr;
@@ -574,13 +574,14 @@ MemoryRegion *flatview_translate(FlatView *fv, hwaddr 
addr, hwaddr *xlat,
     AddressSpace *as = NULL;
 
     /* This can be MMIO, so setup MMIO bit. */
-    section = flatview_do_translate(fv, addr, xlat, plen, NULL,
+    section = flatview_do_translate(fv, addr, xlat, plen_out, NULL,
                                     is_write, true, &as, attrs);
     mr = section.mr;
 
-    if (xen_enabled() && memory_access_is_direct(mr, is_write, attrs)) {
+    if (xen_enabled() && plen_out && memory_access_is_direct(mr, is_write,
+                                                             attrs)) {
         hwaddr page = ((addr & TARGET_PAGE_MASK) + TARGET_PAGE_SIZE) - addr;
-        *plen = MIN(page, *plen);
+        *plen_out = MIN(page, *plen_out);
     }
 
     return mr;
-- 
2.51.0