Re: [PATCH v4 08/84] target/arm: Skip AF and DB updates for AccessType_AT

[Richard Henderson]

On 2/27/26 04:12, Zenghui Yu wrote:
+    /*
+     * For AccessType_AT, DB is not updated (AArch64.SetDirtyFlag),
+     * and it is IMPLEMENTATION DEFINED whether AF is updated
+     * (AArch64.SetAccessFlag; qemu chooses to not update).
+     */
+    if (likely(!ptw->in_at)) {
          /*
           * Access flag.
           * If HA is enabled, prepare to update the descriptor below.

|           * Otherwise, pass the access fault on to software.
|           */
|          if (!(descriptor & (1 << 10))) {
|              if (param.ha) {
|                  new_descriptor |= 1 << 10; /* AF */
|              } else {
|                  fi->type = ARMFault_AccessFlag;
|                  goto do_fault;

This also skips the access flag fault which could be generated by an AT
instruction. Is this an expected change?

Yes.  As mentioned right there in the comment, the access flag fault is IMPLEMENTATION 
DEFINED.


r~