[Qemu-devel] [PATCH v2 06/14] target/arm: Allow SVE to be disabled via a CPU property

[Andrew Jones <drjones@redhat.com>]

Since 97a28b0eeac14 ("target/arm: Allow VFP and Neon to be disabled via
a CPU property") we can disable the 'max' cpu model's VFP and neon
features, but there's no way to disable SVE. Add the 'sve=on|off'
property to give it that flexibility. We also rename
cpu_max_get/set_sve_vq to cpu_max_get/set_sve_max_vq in order for them
to follow the typical *_get/set_<property-name> pattern.

Signed-off-by: Andrew Jones <drjones@redhat.com>
---
 target/arm/cpu.c         | 10 +++++-
 target/arm/cpu64.c       | 72 ++++++++++++++++++++++++++++++++++------
 target/arm/helper.c      |  8 +++--
 target/arm/monitor.c     |  2 +-
 tests/arm-cpu-features.c |  1 +
 5 files changed, 78 insertions(+), 15 deletions(-)

diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index 858f668d226e..f08e178fc84b 100644
--- a/target/arm/cpu.c
+++ b/target/arm/cpu.c
@@ -198,7 +198,7 @@ static void arm_cpu_reset(CPUState *s)
         env->cp15.cpacr_el1 = deposit64(env->cp15.cpacr_el1, 16, 2, 3);
         env->cp15.cptr_el[3] |= CPTR_EZ;
         /* with maximum vector length */
-        env->vfp.zcr_el[1] = cpu->sve_max_vq - 1;
+        env->vfp.zcr_el[1] = cpu->sve_max_vq ? cpu->sve_max_vq - 1 : 0;
         env->vfp.zcr_el[2] = env->vfp.zcr_el[1];
         env->vfp.zcr_el[3] = env->vfp.zcr_el[1];
         /*
@@ -1129,6 +1129,14 @@ static void arm_cpu_realizefn(DeviceState *dev, Error **errp)
         cpu->isar.mvfr0 = u;
     }
 
+    if (!cpu->sve_max_vq) {
+        uint64_t t;
+
+        t = cpu->isar.id_aa64pfr0;
+        t = FIELD_DP64(t, ID_AA64PFR0, SVE, 0);
+        cpu->isar.id_aa64pfr0 = t;
+    }
+
     if (arm_feature(env, ARM_FEATURE_M) && !cpu->has_dsp) {
         uint32_t u;
 
diff --git a/target/arm/cpu64.c b/target/arm/cpu64.c
index 946994838d8a..02ada65f240c 100644
--- a/target/arm/cpu64.c
+++ b/target/arm/cpu64.c
@@ -257,27 +257,75 @@ static void aarch64_a72_initfn(Object *obj)
     define_arm_cp_regs(cpu, cortex_a72_a57_a53_cp_reginfo);
 }
 
-static void cpu_max_get_sve_vq(Object *obj, Visitor *v, const char *name,
-                               void *opaque, Error **errp)
+static void cpu_max_get_sve_max_vq(Object *obj, Visitor *v, const char *name,
+                                   void *opaque, Error **errp)
 {
     ARMCPU *cpu = ARM_CPU(obj);
     visit_type_uint32(v, name, &cpu->sve_max_vq, errp);
 }
 
-static void cpu_max_set_sve_vq(Object *obj, Visitor *v, const char *name,
-                               void *opaque, Error **errp)
+static void cpu_max_set_sve_max_vq(Object *obj, Visitor *v, const char *name,
+                                   void *opaque, Error **errp)
 {
     ARMCPU *cpu = ARM_CPU(obj);
     Error *err = NULL;
+    uint32_t value;
 
-    visit_type_uint32(v, name, &cpu->sve_max_vq, &err);
+    visit_type_uint32(v, name, &value, &err);
+    if (err) {
+        error_propagate(errp, err);
+        return;
+    }
 
-    if (!err && (cpu->sve_max_vq == 0 || cpu->sve_max_vq > ARM_MAX_VQ)) {
-        error_setg(&err, "unsupported SVE vector length");
-        error_append_hint(&err, "Valid sve-max-vq in range [1-%d]\n",
+    if (!cpu->sve_max_vq) {
+        error_setg(errp, "cannot set sve-max-vq");
+        error_append_hint(errp, "SVE has been disabled with sve=off\n");
+        return;
+    }
+
+    cpu->sve_max_vq = value;
+
+    if (cpu->sve_max_vq == 0 || cpu->sve_max_vq > ARM_MAX_VQ) {
+        error_setg(errp, "unsupported SVE vector length");
+        error_append_hint(errp, "Valid sve-max-vq in range [1-%d]\n",
                           ARM_MAX_VQ);
     }
-    error_propagate(errp, err);
+}
+
+static void cpu_arm_get_sve(Object *obj, Visitor *v, const char *name,
+                            void *opaque, Error **errp)
+{
+    ARMCPU *cpu = ARM_CPU(obj);
+    bool value = !!cpu->sve_max_vq;
+
+    visit_type_bool(v, name, &value, errp);
+}
+
+static void cpu_arm_set_sve(Object *obj, Visitor *v, const char *name,
+                            void *opaque, Error **errp)
+{
+    ARMCPU *cpu = ARM_CPU(obj);
+    Error *err = NULL;
+    bool value;
+
+    visit_type_bool(v, name, &value, &err);
+    if (err) {
+        error_propagate(errp, err);
+        return;
+    }
+
+    if (value) {
+        /*
+         * We handle the -cpu <cpu>,sve=off,sve=on case by reinitializing,
+         * but otherwise we don't do anything as an sve=on could come after
+         * a sve-max-vq setting.
+         */
+        if (!cpu->sve_max_vq) {
+            cpu->sve_max_vq = ARM_MAX_VQ;
+        }
+    } else {
+        cpu->sve_max_vq = 0;
+    }
 }
 
 /* -cpu max: if KVM is enabled, like -cpu host (best possible with this host);
@@ -373,8 +421,10 @@ static void aarch64_max_initfn(Object *obj)
 #endif
 
         cpu->sve_max_vq = ARM_MAX_VQ;
-        object_property_add(obj, "sve-max-vq", "uint32", cpu_max_get_sve_vq,
-                            cpu_max_set_sve_vq, NULL, NULL, &error_fatal);
+        object_property_add(obj, "sve-max-vq", "uint32", cpu_max_get_sve_max_vq,
+                            cpu_max_set_sve_max_vq, NULL, NULL, &error_fatal);
+        object_property_add(obj, "sve", "bool", cpu_arm_get_sve,
+                            cpu_arm_set_sve, NULL, NULL, &error_fatal);
     }
 }
 
diff --git a/target/arm/helper.c b/target/arm/helper.c
index edba94004e0b..f500ccb6d31b 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -5314,9 +5314,13 @@ uint32_t sve_zcr_len_for_el(CPUARMState *env, int el)
 static void zcr_write(CPUARMState *env, const ARMCPRegInfo *ri,
                       uint64_t value)
 {
+    ARMCPU *cpu = env_archcpu(env);
     int cur_el = arm_current_el(env);
-    int old_len = sve_zcr_len_for_el(env, cur_el);
-    int new_len;
+    int old_len, new_len;
+
+    assert(cpu->sve_max_vq);
+
+    old_len = sve_zcr_len_for_el(env, cur_el);
 
     /* Bits other than [3:0] are RAZ/WI.  */
     QEMU_BUILD_BUG_ON(ARM_MAX_VQ > 16);
diff --git a/target/arm/monitor.c b/target/arm/monitor.c
index 19e3120eef95..157c487a1551 100644
--- a/target/arm/monitor.c
+++ b/target/arm/monitor.c
@@ -90,7 +90,7 @@ GICCapabilityList *qmp_query_gic_capabilities(Error **errp)
 }
 
 static const char *cpu_model_advertised_features[] = {
-    "aarch64", "pmu",
+    "aarch64", "pmu", "sve",
     NULL
 };
 
diff --git a/tests/arm-cpu-features.c b/tests/arm-cpu-features.c
index 31b1c15bb979..509e458e9c2f 100644
--- a/tests/arm-cpu-features.c
+++ b/tests/arm-cpu-features.c
@@ -158,6 +158,7 @@ static void test_query_cpu_model_expansion(const void *data)
 
     if (g_str_equal(qtest_get_arch(), "aarch64")) {
         assert_has_feature(qts, "max", "aarch64");
+        assert_has_feature(qts, "max", "sve");
         assert_has_feature(qts, "cortex-a57", "pmu");
         assert_has_feature(qts, "cortex-a57", "aarch64");
 
-- 
2.20.1