[PATCH v2] target/arm: Don't skip access flag fault for AccessType_AT

[Zenghui Yu <zenghui.yu@linux.dev>]

As per the pseudo code from DDI0487 M.a.a (on J1-16021) AArch64.S1Walk():

  // Check descriptor AF bit
  elsif (descriptor<10> == '0' && walkparams.ha == '0' &&
          (!accdesc.acctype IN {AccessType_DC, AccessType_IC} ||
           boolean IMPLEMENTATION_DEFINED "Generate access flag fault on IC/DC operations")) then
      fault.statuscode = Fault_AccessFlag;

an access flag fault should be generated for AccessType_AT, if the AF bit
is 0 and !param.ha.

Besides, we should continue to not raise the access flag fault for
in_debug = true which is what we've been doing previously (before commit
efebeec13d07) for LPAE and is what intention of the debugger access
codepath is.

Fixes: efebeec13d07 ("target/arm: Skip AF and DB updates for AccessType_AT")
Signed-off-by: Zenghui Yu <zenghui.yu@linux.dev>
---
* From v1 [1]:
  - handles in_debug = true (Peter)

[1] https://lore.kernel.org/r/20260317122517.47627-1-zenghui.yu@linux.dev

 target/arm/ptw.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/target/arm/ptw.c b/target/arm/ptw.c
index 8b8dc09e72..fa6db9e5a2 100644
--- a/target/arm/ptw.c
+++ b/target/arm/ptw.c
@@ -2118,6 +2118,14 @@ static bool get_phys_addr_lpae(CPUARMState *env, S1Translate *ptw,
     descaddr &= ~(hwaddr)(page_size - 1);
     descaddr |= (address & (page_size - 1));
 
+    if (likely(!ptw->in_debug)) {
+        /* Check descriptor AF bit */
+        if (!(descriptor & (1 << 10)) && !param.ha) {
+            fi->type = ARMFault_AccessFlag;
+            goto do_fault;
+        }
+    }
+
     /*
      * For AccessType_AT, DB is not updated (AArch64.SetDirtyFlag),
      * and it is IMPLEMENTATION DEFINED whether AF is updated
@@ -2127,15 +2135,9 @@ static bool get_phys_addr_lpae(CPUARMState *env, S1Translate *ptw,
         /*
          * 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;
-            }
+        if (!(descriptor & (1 << 10)) && param.ha) {
+            new_descriptor |= 1 << 10; /* AF */
         }
 
         /*
-- 
2.53.0