[PATCH v2 4/6] target/arm: Implement FGWTE3 traps

Reviewed-by: Peter Maydell <[email protected]>
Signed-off-by: Richard Henderson <[email protected]>
---
 target/arm/tcg/op_helper.c     | 40 +++++++++++++++++++++++-----------
 target/arm/tcg/translate-a64.c | 16 +++++++++++++-
 2 files changed, 42 insertions(+), 14 deletions(-)

diff --git a/target/arm/tcg/op_helper.c b/target/arm/tcg/op_helper.c
index c4433be2ed..73cae9b9ad 100644
--- a/target/arm/tcg/op_helper.c
+++ b/target/arm/tcg/op_helper.c
@@ -1066,13 +1066,15 @@ const void *HELPER(access_check_cp_reg)(CPUARMState *env, uint32_t key,
      * Fine-grained traps also are lower priority than undef-to-EL1,
      * higher priority than trap-to-EL3, and we don't care about priority
      * order with other EL2 traps because the syndrome value is the same.
+     *
+     * FGWTE3 traps are exclusively traps to EL3 on registers that are
+     * only accessible to EL3, so there's no possibility of a trap to EL2.
+     * So we can handle these checks here too.
      */
-    if (arm_fgt_active(env, arm_current_el(env))) {
+    if (ri->fgt) {
         uint64_t trapword = 0;
         unsigned int idx = FIELD_EX32(ri->fgt, FGT, IDX);
         unsigned int bitpos = FIELD_EX32(ri->fgt, FGT, BITPOS);
-        bool rev = FIELD_EX32(ri->fgt, FGT, REV);
-        bool nxs = FIELD_EX32(ri->fgt, FGT, NXS);
         bool trapbit;
 
         if (ri->fgt & FGT_EXEC) {
@@ -1085,19 +1087,31 @@ const void *HELPER(access_check_cp_reg)(CPUARMState *env, uint32_t key,
             assert(idx < ARRAY_SIZE(env->cp15.fgt_write));
             trapword = env->cp15.fgt_write[idx];
         }
+        trapbit = extract64(trapword, bitpos, 1);
 
-        if (nxs && (arm_hcrx_el2_eff(env) & HCRX_FGTNXS)) {
+        if ((ri->access & ~PL3_RW) == 0) {
             /*
-             * If HCRX_EL2.FGTnXS is 1 then the fine-grained trap for
-             * TLBI maintenance insns does *not* apply to the nXS variant.
+             * EL3 cpreg -- must be FGWTE3, and FGWTE3_EL3 can only be
+             * set from AArch64, and if the feature is enabled.
              */
-            trapbit = 0;
-        } else {
-            trapbit = extract64(trapword, bitpos, 1);
-        }
-        if (trapbit != rev) {
-            res = CP_ACCESS_TRAP_EL2;
-            goto fail;
+            if (trapbit) {
+                res = CP_ACCESS_TRAP_EL3;
+                goto fail;
+            }
+        } else if (arm_fgt_active(env, arm_current_el(env))) {
+            bool nxs = FIELD_EX32(ri->fgt, FGT, NXS);
+            bool rev = FIELD_EX32(ri->fgt, FGT, REV);
+            if (nxs && (arm_hcrx_el2_eff(env) & HCRX_FGTNXS)) {
+                /*
+                 * If HCRX_EL2.FGTnXS is 1 then the fine-grained trap for
+                 * TLBI maintenance insns does *not* apply to the nXS variant.
+                 */
+                trapbit = 0;
+            }
+            if (trapbit != rev) {
+                res = CP_ACCESS_TRAP_EL2;
+                goto fail;
+            }
         }
     }
 
diff --git a/target/arm/tcg/translate-a64.c b/target/arm/tcg/translate-a64.c
index 1780490065..0931c92307 100644
--- a/target/arm/tcg/translate-a64.c
+++ b/target/arm/tcg/translate-a64.c
@@ -2886,6 +2886,7 @@ static void handle_sys(DisasContext *s, bool isread,
 {
     uint32_t key = ENCODE_AA64_CP_REG(op0, op1, crn, crm, op2);
     const ARMCPRegInfo *ri = get_arm_cp_reginfo(s->cp_regs, key);
+    bool need_helper = false;
     bool need_exit_tb = false;
     bool nv_trap_to_el2 = false;
     bool nv_redirect_reg = false;
@@ -2999,7 +3000,20 @@ static void handle_sys(DisasContext *s, bool isread,
         ri = redirect_cpreg(s, key, isread);
     }
 
-    if (ri->accessfn || (ri->fgt && s->fgt_active)) {
+    if (ri->accessfn) {
+        need_helper = true;
+    } else if (ri->fgt) {
+       /*
+        * EL3-only access means this must be an FGWTE3 trap (which are
+        * always active); otherwise it's an FGT trap to EL2.
+        */
+        if ((ri->access & ~PL3_RW) == 0) {
+            need_helper = dc_isar_feature(aa64_fgwte3, s);
+        } else {
+            need_helper = s->fgt_active;
+        }
+    }
+    if (need_helper) {
         /* Emit code to perform further access permissions checks at
          * runtime; this may result in an exception.
          */
-- 
2.43.0