Re: [PATCH 2/2] memory: suppress INVALID_MEM logs caused by debug access

[Philippe Mathieu-Daudé]

On 14/3/25 08:41, Nicholas Piggin wrote:

Debugger-driven invalid memory accesses are not guest errors, so should
not cause these error logs.

Debuggers can access memory wildly, including access to addresses not
specified by the user (e.g., gdb it might try to walk the stack or load
target addresses to display disassembly). Failure is reported
synchronously by the GDB protcol so the user can be notified via the
debugger client.

Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
  system/memory.c | 37 ++++++++++++++++++++++---------------
  1 file changed, 22 insertions(+), 15 deletions(-)

diff --git a/system/memory.c b/system/memory.c
index 4c829793a0a..960f66e8d7e 100644
--- a/system/memory.c
+++ b/system/memory.c
@@ -1412,18 +1412,23 @@ bool memory_region_access_valid(MemoryRegion *mr,
  {

Should we instead consider debug accesses as always valid? i.e.:

        if (attrs.debug) {
            return true;
        }

      if (mr->ops->valid.accepts
          && !mr->ops->valid.accepts(mr->opaque, addr, size, is_write, attrs)) {
-        qemu_log_mask(LOG_INVALID_MEM, "Invalid %s at addr 0x%" HWADDR_PRIX
-                      ", size %u, region '%s', reason: rejected\n",
-                      is_write ? "write" : "read",
-                      addr, size, memory_region_name(mr));
+        if (attrs.debug) {
+            /* Don't log memory errors due to debugger accesses */
+            qemu_log_mask(LOG_INVALID_MEM, "Invalid %s at addr 0x%" HWADDR_PRIX
+                          ", size %u, region '%s', reason: rejected\n",
+                          is_write ? "write" : "read",
+                          addr, size, memory_region_name(mr));
+        }
          return false;
      }

if (!mr->ops->valid.unaligned && (addr & (size - 1))) {

-        qemu_log_mask(LOG_INVALID_MEM, "Invalid %s at addr 0x%" HWADDR_PRIX
-                      ", size %u, region '%s', reason: unaligned\n",
-                      is_write ? "write" : "read",
-                      addr, size, memory_region_name(mr));
+        if (attrs.debug) {
+            qemu_log_mask(LOG_INVALID_MEM, "Invalid %s at addr 0x%" HWADDR_PRIX
+                          ", size %u, region '%s', reason: unaligned\n",
+                          is_write ? "write" : "read",
+                          addr, size, memory_region_name(mr));
+        }
          return false;
      }

@@ -1434,13 +1439,15 @@ bool memory_region_access_valid(MemoryRegion *mr, if (size > mr->ops->valid.max_access_size

          || size < mr->ops->valid.min_access_size) {
-        qemu_log_mask(LOG_INVALID_MEM, "Invalid %s at addr 0x%" HWADDR_PRIX
-                      ", size %u, region '%s', reason: invalid size "
-                      "(min:%u max:%u)\n",
-                      is_write ? "write" : "read",
-                      addr, size, memory_region_name(mr),
-                      mr->ops->valid.min_access_size,
-                      mr->ops->valid.max_access_size);
+        if (attrs.debug) {
+            qemu_log_mask(LOG_INVALID_MEM, "Invalid %s at addr 0x%" HWADDR_PRIX
+                          ", size %u, region '%s', reason: invalid size "
+                          "(min:%u max:%u)\n",
+                          is_write ? "write" : "read",
+                          addr, size, memory_region_name(mr),
+                          mr->ops->valid.min_access_size,
+                          mr->ops->valid.max_access_size);
+        }
          return false;
      }
      return true;