Re: [PATCH v2 02/17] system/memory: Better describe @plen argument of flatview_translate()

[Thomas Huth]

On 30/09/2025 06.13, Philippe Mathieu-Daudé wrote:

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

Signed-off-by: Philippe Mathieu-Daudé <phi...@linaro.org>
---
  include/system/memory.h | 5 +++--
  system/physmem.c        | 6 +++---
  2 files changed, 6 insertions(+), 5 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..2d1697fce4c 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 +574,13 @@ 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)) {

          hwaddr page = ((addr & TARGET_PAGE_MASK) + TARGET_PAGE_SIZE) - addr;
-        *plen = MIN(page, *plen);
+        *plen_out = MIN(page, *plen_out);

There is no check for a NULL pointer here, so plen_out must *not* be NULL?
Or did I miss something?

 Thomas

      }

return mr;