Merge patch series "make write_misa a no-op and FEATURE_* cleanups"

Daniel Henrique Barboza <dbarboza@ventanamicro.com> says:

The RISCV_FEATURES_* enum and the CPUArchState::features attribute were
introduced 4+ years ago, as a way to retrieve the enabled hart features
that aren't represented via MISA CSR bits. Time passed on, and
RISCVCPUConfig was introduced. With it, we now have a centralized way of
reading all hart features that are enabled/disabled by the user and the
board. All recent features are reading their correspondent cpu->cfg.X
flag.

All but the 5 features in the RISCV_FEATURE_* enum. These features are
still operating in the same way: set it during riscv_cpu_realize() using
their cpu->cfg value, read it using riscv_feature() when needed. There
is nothing special about them in comparison with all the other features
and extensions to justify this special handling.

This series then is doing two things: first we're actually allowing
users to write the MISA CSR if they so choose. Then we're deprecate each
RISC_FEATURE_* usage until, in patch 11, we remove everything related to
it. All 5 existing RISCV_FEATURE_* features will be handled as everyone
else.

* b4-shazam-merge:
  target/riscv/cpu: remove CPUArchState::features and friends
  target/riscv: remove RISCV_FEATURE_MMU
  hw/riscv/virt.c: do not use RISCV_FEATURE_MMU in create_fdt_socket_cpus()
  target/riscv: remove RISCV_FEATURE_PMP
  target/riscv: remove RISCV_FEATURE_EPMP
  target/riscv/cpu.c: error out if EPMP is enabled without PMP
  target/riscv: remove RISCV_FEATURE_DEBUG
  target/riscv: allow MISA writes as experimental
  target/riscv: do not mask unsupported QEMU extensions in write_misa()
  target/riscv: introduce riscv_cpu_cfg()

Message-ID: <20230222185205.355361-1-dbarboza@ventanamicro.com>
[Palmer: use the text from the v1]
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

9 files changed, 39 insertions, 66 deletions

diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c
index 86c4adc..49f2c15 100644
--- a/hw/riscv/virt.c
+++ b/hw/riscv/virt.c
@@ -232,20 +232,21 @@ static void create_fdt_socket_cpus(RISCVVirtState *s, int socket,
     bool is_32_bit = riscv_is_32bit(&s->soc[0]);
 
     for (cpu = s->soc[socket].num_harts - 1; cpu >= 0; cpu--) {
+        RISCVCPU *cpu_ptr = &s->soc[socket].harts[cpu];
+
         cpu_phandle = (*phandle)++;
 
         cpu_name = g_strdup_printf("/cpus/cpu@%d",
             s->soc[socket].hartid_base + cpu);
         qemu_fdt_add_subnode(ms->fdt, cpu_name);
-        if (riscv_feature(&s->soc[socket].harts[cpu].env,
-                          RISCV_FEATURE_MMU)) {
+        if (cpu_ptr->cfg.mmu) {
             qemu_fdt_setprop_string(ms->fdt, cpu_name, "mmu-type",
                                     (is_32_bit) ? "riscv,sv32" : "riscv,sv48");
         } else {
             qemu_fdt_setprop_string(ms->fdt, cpu_name, "mmu-type",
                                     "riscv,none");
         }
-        name = riscv_isa_string(&s->soc[socket].harts[cpu]);
+        name = riscv_isa_string(cpu_ptr);
         qemu_fdt_setprop_string(ms->fdt, cpu_name, "riscv,isa", name);
         g_free(name);
         qemu_fdt_setprop_string(ms->fdt, cpu_name, "compatible", "riscv");
diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index 93b52b8..11da920 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -637,7 +637,7 @@ static void riscv_cpu_reset_hold(Object *obj)
     set_default_nan_mode(1, &env->fp_status);
 
 #ifndef CONFIG_USER_ONLY
-    if (riscv_feature(env, RISCV_FEATURE_DEBUG)) {
+    if (cpu->cfg.debug) {
         riscv_trigger_init(env);
     }
 
@@ -919,24 +919,13 @@ static void riscv_cpu_realize(DeviceState *dev, Error **errp)
         }
     }
 
-    if (cpu->cfg.mmu) {
-        riscv_set_feature(env, RISCV_FEATURE_MMU);
-    }
-
-    if (cpu->cfg.pmp) {
-        riscv_set_feature(env, RISCV_FEATURE_PMP);
-
+    if (cpu->cfg.epmp && !cpu->cfg.pmp) {
         /*
          * Enhanced PMP should only be available
          * on harts with PMP support
          */
-        if (cpu->cfg.epmp) {
-            riscv_set_feature(env, RISCV_FEATURE_EPMP);
-        }
-    }
-
-    if (cpu->cfg.debug) {
-        riscv_set_feature(env, RISCV_FEATURE_DEBUG);
+        error_setg(errp, "Invalid configuration: EPMP requires PMP support");
+        return;
     }
 
 
@@ -1210,6 +1199,12 @@ static Property riscv_cpu_properties[] = {
 
     DEFINE_PROP_BOOL("rvv_ta_all_1s", RISCVCPU, cfg.rvv_ta_all_1s, false),
     DEFINE_PROP_BOOL("rvv_ma_all_1s", RISCVCPU, cfg.rvv_ma_all_1s, false),
+
+    /*
+     * write_misa() is marked as experimental for now so mark
+     * it with -x and default to 'false'.
+     */
+    DEFINE_PROP_BOOL("x-misa-w", RISCVCPU, cfg.misa_w, false),
     DEFINE_PROP_END_OF_LIST(),
 };
 
diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index 31537fc..b9f69a1 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -81,17 +81,6 @@
 #define RVH RV('H')
 #define RVJ RV('J')
 
-/* S extension denotes that Supervisor mode exists, however it is possible
-   to have a core that support S mode but does not have an MMU and there
-   is currently no bit in misa to indicate whether an MMU exists or not
-   so a cpu features bitfield is required, likewise for optional PMP support */
-enum {
-    RISCV_FEATURE_MMU,
-    RISCV_FEATURE_PMP,
-    RISCV_FEATURE_EPMP,
-    RISCV_FEATURE_MISA,
-    RISCV_FEATURE_DEBUG
-};
 
 /* Privileged specification version */
 enum {
@@ -186,8 +175,6 @@ struct CPUArchState {
     /* 128-bit helpers upper part return value */
     target_ulong retxh;
 
-    uint32_t features;
-
 #ifdef CONFIG_USER_ONLY
     uint32_t elf_flags;
 #endif
@@ -498,6 +485,7 @@ struct RISCVCPUConfig {
     bool pmp;
     bool epmp;
     bool debug;
+    bool misa_w;
 
     bool short_isa_string;
 };
@@ -535,16 +523,6 @@ static inline int riscv_has_ext(CPURISCVState *env, target_ulong ext)
     return (env->misa_ext & ext) != 0;
 }
 
-static inline bool riscv_feature(CPURISCVState *env, int feature)
-{
-    return env->features & (1ULL << feature);
-}
-
-static inline void riscv_set_feature(CPURISCVState *env, int feature)
-{
-    env->features |= (1ULL << feature);
-}
-
 #include "cpu_user.h"
 
 extern const char * const riscv_int_regnames[];
@@ -654,6 +632,11 @@ static inline RISCVMXL riscv_cpu_mxl(CPURISCVState *env)
 #endif
 #define riscv_cpu_mxl_bits(env) (1UL << (4 + riscv_cpu_mxl(env)))
 
+static inline const RISCVCPUConfig *riscv_cpu_cfg(CPURISCVState *env)
+{
+    return &env_archcpu(env)->cfg;
+}
+
 #if defined(TARGET_RISCV32)
 #define cpu_recompute_xl(env)  ((void)(env), MXL_RV32)
 #else
diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
index 3a9472a..2b731a8 100644
--- a/target/riscv/cpu_helper.c
+++ b/target/riscv/cpu_helper.c
@@ -105,7 +105,7 @@ void cpu_get_tb_cpu_state(CPURISCVState *env, target_ulong *pc,
         flags = FIELD_DP32(flags, TB_FLAGS, MSTATUS_HS_VS,
                            get_field(env->mstatus_hs, MSTATUS_VS));
     }
-    if (riscv_feature(env, RISCV_FEATURE_DEBUG) && !icount_enabled()) {
+    if (cpu->cfg.debug && !icount_enabled()) {
         flags = FIELD_DP32(flags, TB_FLAGS, ITRIGGER, env->itrigger_enabled);
     }
 #endif
@@ -706,7 +706,7 @@ static int get_physical_address_pmp(CPURISCVState *env, int *prot,
     pmp_priv_t pmp_priv;
     int pmp_index = -1;
 
-    if (!riscv_feature(env, RISCV_FEATURE_PMP)) {
+    if (!riscv_cpu_cfg(env)->pmp) {
         *prot = PAGE_READ | PAGE_WRITE | PAGE_EXEC;
         return TRANSLATE_SUCCESS;
     }
@@ -796,7 +796,7 @@ static int get_physical_address(CPURISCVState *env, hwaddr *physical,
         mode = PRV_U;
     }
 
-    if (mode == PRV_M || !riscv_feature(env, RISCV_FEATURE_MMU)) {
+    if (mode == PRV_M || !riscv_cpu_cfg(env)->mmu) {
         *physical = addr;
         *prot = PAGE_READ | PAGE_WRITE | PAGE_EXEC;
         return TRANSLATE_SUCCESS;
diff --git a/target/riscv/csr.c b/target/riscv/csr.c
index 1b0a0c1..75a540b 100644
--- a/target/riscv/csr.c
+++ b/target/riscv/csr.c
@@ -419,7 +419,7 @@ static int aia_hmode32(CPURISCVState *env, int csrno)
 
 static RISCVException pmp(CPURISCVState *env, int csrno)
 {
-    if (riscv_feature(env, RISCV_FEATURE_PMP)) {
+    if (riscv_cpu_cfg(env)->pmp) {
         return RISCV_EXCP_NONE;
     }
 
@@ -428,7 +428,7 @@ static RISCVException pmp(CPURISCVState *env, int csrno)
 
 static RISCVException epmp(CPURISCVState *env, int csrno)
 {
-    if (env->priv == PRV_M && riscv_feature(env, RISCV_FEATURE_EPMP)) {
+    if (env->priv == PRV_M && riscv_cpu_cfg(env)->epmp) {
         return RISCV_EXCP_NONE;
     }
 
@@ -437,7 +437,7 @@ static RISCVException epmp(CPURISCVState *env, int csrno)
 
 static RISCVException debug(CPURISCVState *env, int csrno)
 {
-    if (riscv_feature(env, RISCV_FEATURE_DEBUG)) {
+    if (riscv_cpu_cfg(env)->debug) {
         return RISCV_EXCP_NONE;
     }
 
@@ -1329,7 +1329,7 @@ static RISCVException read_misa(CPURISCVState *env, int csrno,
 static RISCVException write_misa(CPURISCVState *env, int csrno,
                                  target_ulong val)
 {
-    if (!riscv_feature(env, RISCV_FEATURE_MISA)) {
+    if (!riscv_cpu_cfg(env)->misa_w) {
         /* drop write to misa */
         return RISCV_EXCP_NONE;
     }
@@ -1356,9 +1356,6 @@ static RISCVException write_misa(CPURISCVState *env, int csrno,
     /* Mask extensions that are not supported by this hart */
     val &= env->misa_ext_mask;
 
-    /* Mask extensions that are not supported by QEMU */
-    val &= (RVI | RVE | RVM | RVA | RVF | RVD | RVC | RVS | RVU | RVV);
-
     /* 'D' depends on 'F', so clear 'D' if 'F' is not present */
     if ((val & RVD) && !(val & RVF)) {
         val &= ~RVD;
@@ -2624,7 +2621,7 @@ static RISCVException rmw_siph(CPURISCVState *env, int csrno,
 static RISCVException read_satp(CPURISCVState *env, int csrno,
                                 target_ulong *val)
 {
-    if (!riscv_feature(env, RISCV_FEATURE_MMU)) {
+    if (!riscv_cpu_cfg(env)->mmu) {
         *val = 0;
         return RISCV_EXCP_NONE;
     }
@@ -2643,7 +2640,7 @@ static RISCVException write_satp(CPURISCVState *env, int csrno,
 {
     target_ulong vm, mask;
 
-    if (!riscv_feature(env, RISCV_FEATURE_MMU)) {
+    if (!riscv_cpu_cfg(env)->mmu) {
         return RISCV_EXCP_NONE;
     }
 
diff --git a/target/riscv/machine.c b/target/riscv/machine.c
index c6ce318..9c45593 100644
--- a/target/riscv/machine.c
+++ b/target/riscv/machine.c
@@ -27,9 +27,8 @@
 static bool pmp_needed(void *opaque)
 {
     RISCVCPU *cpu = opaque;
-    CPURISCVState *env = &cpu->env;
 
-    return riscv_feature(env, RISCV_FEATURE_PMP);
+    return cpu->cfg.pmp;
 }
 
 static int pmp_post_load(void *opaque, int version_id)
@@ -226,9 +225,8 @@ static const VMStateDescription vmstate_kvmtimer = {
 static bool debug_needed(void *opaque)
 {
     RISCVCPU *cpu = opaque;
-    CPURISCVState *env = &cpu->env;
 
-    return riscv_feature(env, RISCV_FEATURE_DEBUG);
+    return cpu->cfg.debug;
 }
 
 static int debug_post_load(void *opaque, int version_id)
@@ -333,8 +331,8 @@ static const VMStateDescription vmstate_pmu_ctr_state = {
 
 const VMStateDescription vmstate_riscv_cpu = {
     .name = "cpu",
-    .version_id = 6,
-    .minimum_version_id = 6,
+    .version_id = 7,
+    .minimum_version_id = 7,
     .post_load = riscv_cpu_post_load,
     .fields = (VMStateField[]) {
         VMSTATE_UINTTL_ARRAY(env.gpr, RISCVCPU, 32),
@@ -353,7 +351,6 @@ const VMStateDescription vmstate_riscv_cpu = {
         VMSTATE_UINT32(env.misa_ext, RISCVCPU),
         VMSTATE_UINT32(env.misa_mxl_max, RISCVCPU),
         VMSTATE_UINT32(env.misa_ext_mask, RISCVCPU),
-        VMSTATE_UINT32(env.features, RISCVCPU),
         VMSTATE_UINTTL(env.priv, RISCVCPU),
         VMSTATE_UINTTL(env.virt, RISCVCPU),
         VMSTATE_UINT64(env.resetvec, RISCVCPU),
diff --git a/target/riscv/monitor.c b/target/riscv/monitor.c
index 236f93b..f36ddfa 100644
--- a/target/riscv/monitor.c
+++ b/target/riscv/monitor.c
@@ -218,7 +218,7 @@ void hmp_info_mem(Monitor *mon, const QDict *qdict)
         return;
     }
 
-    if (!riscv_feature(env, RISCV_FEATURE_MMU)) {
+    if (!riscv_cpu_cfg(env)->mmu) {
         monitor_printf(mon, "S-mode MMU unavailable\n");
         return;
     }
diff --git a/target/riscv/op_helper.c b/target/riscv/op_helper.c
index 48f918b..9c0b91c 100644
--- a/target/riscv/op_helper.c
+++ b/target/riscv/op_helper.c
@@ -195,7 +195,7 @@ target_ulong helper_mret(CPURISCVState *env)
     uint64_t mstatus = env->mstatus;
     target_ulong prev_priv = get_field(mstatus, MSTATUS_MPP);
 
-    if (riscv_feature(env, RISCV_FEATURE_PMP) &&
+    if (riscv_cpu_cfg(env)->pmp &&
         !pmp_get_num_rules(env) && (prev_priv != PRV_M)) {
         riscv_raise_exception(env, RISCV_EXCP_INST_ACCESS_FAULT, GETPC());
     }
diff --git a/target/riscv/pmp.c b/target/riscv/pmp.c
index 4bc4113..a08cd95 100644
--- a/target/riscv/pmp.c
+++ b/target/riscv/pmp.c
@@ -88,7 +88,7 @@ static void pmp_write_cfg(CPURISCVState *env, uint32_t pmp_index, uint8_t val)
     if (pmp_index < MAX_RISCV_PMPS) {
         bool locked = true;
 
-        if (riscv_feature(env, RISCV_FEATURE_EPMP)) {
+        if (riscv_cpu_cfg(env)->epmp) {
             /* mseccfg.RLB is set */
             if (MSECCFG_RLB_ISSET(env)) {
                 locked = false;
@@ -239,7 +239,7 @@ static bool pmp_hart_has_privs_default(CPURISCVState *env, target_ulong addr,
 {
     bool ret;
 
-    if (riscv_feature(env, RISCV_FEATURE_EPMP)) {
+    if (riscv_cpu_cfg(env)->epmp) {
         if (MSECCFG_MMWP_ISSET(env)) {
             /*
              * The Machine Mode Whitelist Policy (mseccfg.MMWP) is set
@@ -265,7 +265,7 @@ static bool pmp_hart_has_privs_default(CPURISCVState *env, target_ulong addr,
         }
     }
 
-    if ((!riscv_feature(env, RISCV_FEATURE_PMP)) || (mode == PRV_M)) {
+    if (!riscv_cpu_cfg(env)->pmp || (mode == PRV_M)) {
         /*
          * Privileged spec v1.10 states if HW doesn't implement any PMP entry
          * or no PMP entry matches an M-Mode access, the access succeeds.
@@ -315,7 +315,7 @@ int pmp_hart_has_privs(CPURISCVState *env, target_ulong addr,
     }
 
     if (size == 0) {
-        if (riscv_feature(env, RISCV_FEATURE_MMU)) {
+        if (riscv_cpu_cfg(env)->mmu) {
             /*
              * If size is unknown (0), assume that all bytes
              * from addr to the end of the page will be accessed.