[PATCH v6 13/14] target/arm: Implement FEAT_HAFDBS, dirty bit portion

[Richard Henderson]

Perform the atomic update for hardware management of the dirty bit.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
v5: Move the DB update before attributes are extracted and merged.
---
 target/arm/cpu64.c |  2 +-
 target/arm/ptw.c   | 16 ++++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/target/arm/cpu64.c b/target/arm/cpu64.c
index fe1369fe96..0732796559 100644
--- a/target/arm/cpu64.c
+++ b/target/arm/cpu64.c
@@ -1165,7 +1165,7 @@ static void aarch64_max_initfn(Object *obj)
     cpu->isar.id_aa64mmfr0 = t;
 
     t = cpu->isar.id_aa64mmfr1;
-    t = FIELD_DP64(t, ID_AA64MMFR1, HAFDBS, 1);   /* FEAT_HAFDBS, AF only */
+    t = FIELD_DP64(t, ID_AA64MMFR1, HAFDBS, 2);   /* FEAT_HAFDBS */
     t = FIELD_DP64(t, ID_AA64MMFR1, VMIDBITS, 2); /* FEAT_VMID16 */
     t = FIELD_DP64(t, ID_AA64MMFR1, VH, 1);       /* FEAT_VHE */
     t = FIELD_DP64(t, ID_AA64MMFR1, HPDS, 1);     /* FEAT_HPDS */
diff --git a/target/arm/ptw.c b/target/arm/ptw.c
index d9f89b6105..d87757a700 100644
--- a/target/arm/ptw.c
+++ b/target/arm/ptw.c
@@ -1463,6 +1463,22 @@ static bool get_phys_addr_lpae(CPUARMState *env, 
S1Translate *ptw,
                 goto do_fault;
             }
         }
+
+        /*
+         * Dirty Bit.
+         * If HD is enabled, pre-emptively set/clear the appropriate AP/S2AP
+         * bit for writeback. The actual write protection test may still be
+         * overridden by tableattrs, to be merged below.
+         */
+        if (param.hd
+            && extract64(descriptor, 51, 1)  /* DBM */
+            && access_type == MMU_DATA_STORE) {
+            if (regime_is_stage2(mmu_idx)) {
+                new_descriptor |= 1ull << 7;    /* set S2AP[1] */
+            } else {
+                new_descriptor &= ~(1ull << 7); /* clear AP[2] */
+            }
+        }
     }
 
     /*
-- 
2.34.1