commit efebeec13d076100191a4a5a98f047c46c0d592c
author Richard Henderson <richard.henderson@linaro.org> Sat Aug 30 15:40:12 2025 +1000
committer Peter Maydell <peter.maydell@linaro.org> Tue Sep 16 17:31:53 2025 +0100
tree 8f7f37903b8dc9266b7200dd19ad6c6b341ce572
parent 8818b2d91363dc6b478edc4e6325e958e7348648

target/arm: Skip AF and DB updates for AccessType_AT

We are required to skip DB update for AT instructions, and
we are allowed to skip AF updates.  Choose to skip both.

Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20250830054128.448363-9-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target/arm/ptw.c

diff --git a/target/arm/ptw.c b/target/arm/ptw.c
index 8925c9a..089eeff 100644
--- a/target/arm/ptw.c
+++ b/target/arm/ptw.c
@@ -59,6 +59,12 @@
      */
     bool in_debug;
     /*
+     * in_at: is this AccessType_AT?
+     * This is also set for debug, because at heart that is also
+     * an address translation, and simplifies a test.
+     */
+    bool in_at;
+    /*
      * If this is stage 2 of a stage 1+2 page table walk, then this must
      * be true if stage 1 is an EL0 access; otherwise this is ignored.
      * Stage 2 is indicated by in_mmu_idx set to ARMMMUIdx_Stage2{,_S}.
@@ -1929,7 +1935,12 @@
     descaddr &= ~(hwaddr)(page_size - 1);
     descaddr |= (address & (page_size - 1));
 
-    if (likely(!ptw->in_debug)) {
+    /*
+     * 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.
@@ -3553,6 +3564,7 @@
     S1Translate ptw = {
         .in_mmu_idx = mmu_idx,
         .in_space = space,
+        .in_at = true,
         .in_prot_check = prot_check,
     };
     /*
@@ -3653,6 +3665,7 @@
         .in_mmu_idx = mmu_idx,
         .in_space = arm_mmu_idx_to_security_space(env, mmu_idx),
         .in_debug = true,
+        .in_at = true,
         .in_prot_check = 0,
     };
     GetPhysAddrResult res = {};