target/riscv: rework 'priv_spec'

'priv_spec' and 'vext_spec' are two string options used as a fancy way
of setting integers in the CPU state (cpu->env.priv_ver and
cpu->env.vext_ver). It requires us to deal with string parsing and to
store them in cpu_cfg.

We must support these string options, but we don't need to store them.
We have a precedence for this kind of arrangement in target/ppc/compat.c,
ppc_compat_prop_get|set, getters and setters used for the
'max-cpu-compat' class property of the pseries ppc64 machine. We'll do
the same with both 'priv_spec' and 'vext_spec'.

For 'priv_spec', the validation from riscv_cpu_validate_priv_spec() will
be done by the prop_priv_spec_set() setter, while also preventing it to
be changed for vendor CPUs. Add two helpers that converts env->priv_ver
back and forth to its string representation. These helpers allow us to
get a string and set 'env->priv_ver' and return a string giving the
current env->priv_ver value. In other words, make the cpu->cfg.priv_spec
string obsolete.

Last but not the least, move the reworked 'priv_spec' option to
riscv_cpu_properties[].

After all said and done, we don't need to store the 'priv_spec' string in
the CPU state, and we're now protecting vendor CPUs from priv_ver
changes:

$ ./build/qemu-system-riscv64 -M virt -cpu sifive-e51,priv_spec="v1.12.0"
qemu-system-riscv64: can't apply global sifive-e51-riscv-cpu.priv_spec=v1.12.0:
    CPU 'sifive-e51' does not allow changing the value of 'priv_spec'
Current 'priv_spec' val: v1.10.0
$

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Tested-by: Vladimir Isaev <vladimir.isaev@syntacore.com>
Message-ID: <20240105230546.265053-7-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/cpu.c

@@ -1686,8 +1686,77 @@ static const PropertyInfo prop_pmp = {
     .set = prop_pmp_set,
 };
 
+static int priv_spec_from_str(const char *priv_spec_str)
+{
+    int priv_version = -1;
+
+    if (!g_strcmp0(priv_spec_str, PRIV_VER_1_12_0_STR)) {
+        priv_version = PRIV_VERSION_1_12_0;
+    } else if (!g_strcmp0(priv_spec_str, PRIV_VER_1_11_0_STR)) {
+        priv_version = PRIV_VERSION_1_11_0;
+    } else if (!g_strcmp0(priv_spec_str, PRIV_VER_1_10_0_STR)) {
+        priv_version = PRIV_VERSION_1_10_0;
+    }
+
+    return priv_version;
+}
+
+static const char *priv_spec_to_str(int priv_version)
+{
+    switch (priv_version) {
+    case PRIV_VERSION_1_10_0:
+        return PRIV_VER_1_10_0_STR;
+    case PRIV_VERSION_1_11_0:
+        return PRIV_VER_1_11_0_STR;
+    case PRIV_VERSION_1_12_0:
+        return PRIV_VER_1_12_0_STR;
+    default:
+        return NULL;
+    }
+}
+
+static void prop_priv_spec_set(Object *obj, Visitor *v, const char *name,
+                               void *opaque, Error **errp)
+{
+    RISCVCPU *cpu = RISCV_CPU(obj);
+    g_autofree char *value = NULL;
+    int priv_version = -1;
+
+    visit_type_str(v, name, &value, errp);
+
+    priv_version = priv_spec_from_str(value);
+    if (priv_version < 0) {
+        error_setg(errp, "Unsupported privilege spec version '%s'", value);
+        return;
+    }
+
+    if (priv_version != cpu->env.priv_ver && riscv_cpu_is_vendor(obj)) {
+        cpu_set_prop_err(cpu, name, errp);
+        error_append_hint(errp, "Current '%s' val: %s\n", name,
+                          object_property_get_str(obj, name, NULL));
+        return;
+    }
+
+    cpu_option_add_user_setting(name, priv_version);
+    cpu->env.priv_ver = priv_version;
+}
+
+static void prop_priv_spec_get(Object *obj, Visitor *v, const char *name,
+                               void *opaque, Error **errp)
+{
+    RISCVCPU *cpu = RISCV_CPU(obj);
+    const char *value = priv_spec_to_str(cpu->env.priv_ver);
+
+    visit_type_str(v, name, (char **)&value, errp);
+}
+
+static const PropertyInfo prop_priv_spec = {
+    .name = "priv_spec",
+    .get = prop_priv_spec_get,
+    .set = prop_priv_spec_set,
+};
+
 Property riscv_cpu_options[] = {
-    DEFINE_PROP_STRING("priv_spec", RISCVCPU, cfg.priv_spec),
     DEFINE_PROP_STRING("vext_spec", RISCVCPU, cfg.vext_spec),
 
     DEFINE_PROP_UINT16("vlen", RISCVCPU, cfg.vlen, 128),
@@ -1776,6 +1845,8 @@ static Property riscv_cpu_properties[] = {
     {.name = "mmu", .info = &prop_mmu},
     {.name = "pmp", .info = &prop_pmp},
 
+    {.name = "priv_spec", .info = &prop_priv_spec},
+
 #ifndef CONFIG_USER_ONLY
     DEFINE_PROP_UINT64("resetvec", RISCVCPU, env.resetvec, DEFAULT_RSTVEC),
 #endif

target/riscv/cpu.h

@@ -94,6 +94,9 @@ typedef struct riscv_cpu_profile {
 extern RISCVCPUProfile *riscv_profiles[];
 
 /* Privileged specification version */
+#define PRIV_VER_1_10_0_STR "v1.10.0"
+#define PRIV_VER_1_11_0_STR "v1.11.0"
+#define PRIV_VER_1_12_0_STR "v1.12.0"
 enum {
     PRIV_VERSION_1_10_0 = 0,
     PRIV_VERSION_1_11_0,

target/riscv/cpu_cfg.h

@@ -139,7 +139,6 @@ struct RISCVCPUConfig {
     bool ext_XVentanaCondOps;
 
     uint32_t pmu_mask;
-    char *priv_spec;
     char *vext_spec;
     uint16_t vlen;
     uint16_t elen;

target/riscv/tcg/tcg-cpu.c

@@ -295,29 +295,6 @@ static void riscv_cpu_validate_misa_mxl(RISCVCPU *cpu, Error **errp)
     }
 }
 
-static void riscv_cpu_validate_priv_spec(RISCVCPU *cpu, Error **errp)
-{
-    CPURISCVState *env = &cpu->env;
-    int priv_version = -1;
-
-    if (cpu->cfg.priv_spec) {
-        if (!g_strcmp0(cpu->cfg.priv_spec, "v1.12.0")) {
-            priv_version = PRIV_VERSION_1_12_0;
-        } else if (!g_strcmp0(cpu->cfg.priv_spec, "v1.11.0")) {
-            priv_version = PRIV_VERSION_1_11_0;
-        } else if (!g_strcmp0(cpu->cfg.priv_spec, "v1.10.0")) {
-            priv_version = PRIV_VERSION_1_10_0;
-        } else {
-            error_setg(errp,
-                       "Unsupported privilege spec version '%s'",
-                       cpu->cfg.priv_spec);
-            return;
-        }
-
-        env->priv_ver = priv_version;
-    }
-}
-
 static void riscv_cpu_validate_v(CPURISCVState *env, RISCVCPUConfig *cfg,
                                  Error **errp)
 {
@@ -909,12 +886,6 @@ void riscv_tcg_cpu_finalize_features(RISCVCPU *cpu, Error **errp)
     CPURISCVState *env = &cpu->env;
     Error *local_err = NULL;
 
-    riscv_cpu_validate_priv_spec(cpu, &local_err);
-    if (local_err != NULL) {
-        error_propagate(errp, local_err);
-        return;
-    }
-
     riscv_cpu_validate_misa_priv(env, &local_err);
     if (local_err != NULL) {
         error_propagate(errp, local_err);