[PATCH v2 5/6] target/riscv: Gate hardware A/D PTE bit updating

[Andrew Jones <ajones@ventanamicro.com>]

Gate hardware A/D PTE bit updating on {m,h}envcfg.ADUE and only
enable menvcfg.ADUE on reset if svade has not been selected. Now
that we also consider svade, we have four possible configurations:

 1) !svade && !svadu
    use hardware updating and there's no way to disable it
    (the default, which maintains past behavior. Maintaining
     the default, even with !svadu is a change that fixes [1])

 2) !svade && svadu
    use hardware updating, but also provide {m,h}envcfg.ADUE,
    allowing software to switch to exception mode
    (being able to switch is a change which fixes [1])

 3) svade && !svadu
    use exception mode and there's no way to switch to hardware
    updating
    (this behavior change fixes [2])

 4) svade && svadu
    use exception mode, but also provide {m,h}envcfg.ADUE,
    allowing software to switch to hardware updating
    (this behavior change fixes [2])

Fixes: 0af3f115e68e ("target/riscv: Add *envcfg.HADE related check in address translation") [1]
Fixes: 48531f5adb2a ("target/riscv: implement svade") [2]
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
---
 target/riscv/cpu.c         |  2 +-
 target/riscv/cpu_helper.c  | 18 ++++++++++++++----
 target/riscv/tcg/tcg-cpu.c | 16 +++++-----------
 3 files changed, 20 insertions(+), 16 deletions(-)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index 7fd433daee74..a56c2ff91d6d 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -960,7 +960,7 @@ static void riscv_cpu_reset_hold(Object *obj)
     env->two_stage_lookup = false;
 
     env->menvcfg = (cpu->cfg.ext_svpbmt ? MENVCFG_PBMTE : 0) |
-                   (cpu->cfg.ext_svadu ? MENVCFG_ADUE : 0);
+                   (!cpu->cfg.ext_svade && cpu->cfg.ext_svadu ? MENVCFG_ADUE : 0);
     env->henvcfg = 0;
 
     /* Initialized default priorities of local interrupts. */
diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
index 8da9104da450..9da9758cb4d4 100644
--- a/target/riscv/cpu_helper.c
+++ b/target/riscv/cpu_helper.c
@@ -907,7 +907,9 @@ static int get_physical_address(CPURISCVState *env, hwaddr *physical,
     }
 
     bool pbmte = env->menvcfg & MENVCFG_PBMTE;
-    bool adue = env->menvcfg & MENVCFG_ADUE;
+    bool svade = riscv_cpu_cfg(env)->ext_svade;
+    bool svadu = riscv_cpu_cfg(env)->ext_svadu;
+    bool adue = svadu ? env->menvcfg & MENVCFG_ADUE : !svade;
 
     if (first_stage && two_stage && env->virt_enabled) {
         pbmte = pbmte && (env->henvcfg & HENVCFG_PBMTE);
@@ -1082,9 +1084,17 @@ restart:
         return TRANSLATE_FAIL;
     }
 
-    /* If necessary, set accessed and dirty bits. */
-    target_ulong updated_pte = pte | PTE_A |
-                (access_type == MMU_DATA_STORE ? PTE_D : 0);
+    target_ulong updated_pte = pte;
+
+    /*
+     * If ADUE is enabled, set accessed and dirty bits.
+     * Otherwise raise an exception if necessary.
+     */
+    if (adue) {
+        updated_pte |= PTE_A | (access_type == MMU_DATA_STORE ? PTE_D : 0);
+    } else if (!(pte & PTE_A) || (access_type == MMU_DATA_STORE && !(pte & PTE_D))) {
+        return TRANSLATE_FAIL;
+    }
 
     /* Page table updates need to be atomic with MTTCG enabled */
     if (updated_pte != pte && !is_debug) {
diff --git a/target/riscv/tcg/tcg-cpu.c b/target/riscv/tcg/tcg-cpu.c
index 6d5028cf84d0..bc3c45b11704 100644
--- a/target/riscv/tcg/tcg-cpu.c
+++ b/target/riscv/tcg/tcg-cpu.c
@@ -196,18 +196,14 @@ static bool cpu_cfg_offset_is_named_feat(uint32_t ext_offset)
 
 static void riscv_cpu_enable_named_feat(RISCVCPU *cpu, uint32_t feat_offset)
 {
-    switch (feat_offset) {
-    case CPU_CFG_OFFSET(ext_zic64b):
+     /*
+      * All other named features are already enabled
+      * in riscv_tcg_cpu_instance_init().
+      */
+    if (feat_offset == CPU_CFG_OFFSET(ext_zic64b)) {
         cpu->cfg.cbom_blocksize = 64;
         cpu->cfg.cbop_blocksize = 64;
         cpu->cfg.cboz_blocksize = 64;
-        break;
-    case CPU_CFG_OFFSET(ext_svade):
-        cpu->cfg.ext_svadu = false;
-        break;
-    default:
-        /* Named feature already enabled in riscv_tcg_cpu_instance_init */
-        return;
     }
 }
 
@@ -349,8 +345,6 @@ static void riscv_cpu_update_named_features(RISCVCPU *cpu)
     cpu->cfg.ext_zic64b = cpu->cfg.cbom_blocksize == 64 &&
                           cpu->cfg.cbop_blocksize == 64 &&
                           cpu->cfg.cboz_blocksize == 64;
-
-    cpu->cfg.ext_svade = !cpu->cfg.ext_svadu;
 }
 
 static void riscv_cpu_validate_g(RISCVCPU *cpu)
-- 
2.43.0