target/arm: Implement SMSTART, SMSTOP

These two instructions are aliases of MSR (immediate).
Use the two helpers to properly implement svcr_write.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20220620175235.60881-11-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target/arm/cpu.h

@@ -1120,6 +1120,7 @@ void aarch64_sve_change_el(CPUARMState *env, int old_el,
                            int new_el, bool el0_a64);
 void aarch64_add_sve_properties(Object *obj);
 void aarch64_add_pauth_properties(Object *obj);
+void arm_reset_sve_state(CPUARMState *env);
 
 /*
  * SVE registers are encoded in KVM's memory in an endianness-invariant format.

target/arm/helper-sme.h

@@ -0,0 +1,21 @@
+/*
+ *  AArch64 SME specific helper definitions
+ *
+ *  Copyright (c) 2022 Linaro, Ltd
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+DEF_HELPER_FLAGS_2(set_pstate_sm, TCG_CALL_NO_RWG, void, env, i32)
+DEF_HELPER_FLAGS_2(set_pstate_za, TCG_CALL_NO_RWG, void, env, i32)

target/arm/helper.c

@@ -6366,9 +6366,9 @@ static CPAccessResult access_esm(CPUARMState *env, const ARMCPRegInfo *ri,
 static void svcr_write(CPUARMState *env, const ARMCPRegInfo *ri,
                        uint64_t value)
 {
-    value &= R_SVCR_SM_MASK | R_SVCR_ZA_MASK;
-    /* TODO: Side effects. */
-    env->svcr = value;
+    helper_set_pstate_sm(env, FIELD_EX64(value, SVCR, SM));
+    helper_set_pstate_za(env, FIELD_EX64(value, SVCR, ZA));
+    arm_rebuild_hflags(env);
 }
 
 static void smcr_write(CPUARMState *env, const ARMCPRegInfo *ri,

target/arm/helper.h

@@ -1022,6 +1022,7 @@ DEF_HELPER_FLAGS_6(gvec_bfmlal_idx, TCG_CALL_NO_RWG,
 #ifdef TARGET_AARCH64
 #include "helper-a64.h"
 #include "helper-sve.h"
+#include "helper-sme.h"
 #endif
 
 #include "helper-mve.h"

target/arm/meson.build

@@ -47,6 +47,7 @@ arm_ss.add(when: 'TARGET_AARCH64', if_true: files(
   'mte_helper.c',
   'pauth_helper.c',
   'sve_helper.c',
+  'sme_helper.c',
   'translate-a64.c',
   'translate-sve.c',
 ))

target/arm/sme_helper.c

@@ -0,0 +1,61 @@
+/*
+ * ARM SME Operations
+ *
+ * Copyright (c) 2022 Linaro, Ltd.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "qemu/osdep.h"
+#include "cpu.h"
+#include "internals.h"
+#include "exec/helper-proto.h"
+
+/* ResetSVEState */
+void arm_reset_sve_state(CPUARMState *env)
+{
+    memset(env->vfp.zregs, 0, sizeof(env->vfp.zregs));
+    /* Recall that FFR is stored as pregs[16]. */
+    memset(env->vfp.pregs, 0, sizeof(env->vfp.pregs));
+    vfp_set_fpcr(env, 0x0800009f);
+}
+
+void helper_set_pstate_sm(CPUARMState *env, uint32_t i)
+{
+    if (i == FIELD_EX64(env->svcr, SVCR, SM)) {
+        return;
+    }
+    env->svcr ^= R_SVCR_SM_MASK;
+    arm_reset_sve_state(env);
+}
+
+void helper_set_pstate_za(CPUARMState *env, uint32_t i)
+{
+    if (i == FIELD_EX64(env->svcr, SVCR, ZA)) {
+        return;
+    }
+    env->svcr ^= R_SVCR_ZA_MASK;
+
+    /*
+     * ResetSMEState.
+     *
+     * SetPSTATE_ZA zeros on enable and disable.  We can zero this only
+     * on enable: while disabled, the storage is inaccessible and the
+     * value does not matter.  We're not saving the storage in vmstate
+     * when disabled either.
+     */
+    if (i) {
+        memset(env->zarray, 0, sizeof(env->zarray));
+    }
+}

target/arm/translate-a64.c

@@ -1762,6 +1762,30 @@ static void handle_msr_i(DisasContext *s, uint32_t insn,
         }
         break;
 
+    case 0x1b: /* SVCR* */
+        if (!dc_isar_feature(aa64_sme, s) || crm < 2 || crm > 7) {
+            goto do_unallocated;
+        }
+        if (sme_access_check(s)) {
+            bool i = crm & 1;
+            bool changed = false;
+
+            if ((crm & 2) && i != s->pstate_sm) {
+                gen_helper_set_pstate_sm(cpu_env, tcg_constant_i32(i));
+                changed = true;
+            }
+            if ((crm & 4) && i != s->pstate_za) {
+                gen_helper_set_pstate_za(cpu_env, tcg_constant_i32(i));
+                changed = true;
+            }
+            if (changed) {
+                gen_rebuild_hflags(s);
+            } else {
+                s->base.is_jmp = DISAS_NEXT;
+            }
+        }
+        break;
+
     default:
     do_unallocated:
         unallocated_encoding(s);