[PATCH v2 12/13] target/riscv: Add a preferred ISA extension rule

[Atish Patra]

In addition to the implied rule, a preferred rule will be useful
where an ISA extension may require a list of ISA extension to be
enabled to use all the features defined in that extension. All
these extensions may not be implied in the ISA.

This patch just introduces a new preferred rule which allows
to enable multiple extensions together without burdening the qemu
commandline user.

Signed-off-by: Atish Patra <atishp@rivosinc.com>
---
 target/riscv/cpu.c         |  4 ++++
 target/riscv/cpu.h         | 17 ++++++++++++++
 target/riscv/tcg/tcg-cpu.c | 57 ++++++++++++++++++++++++++++++++++++++++------
 3 files changed, 71 insertions(+), 7 deletions(-)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index 393d1d67120e..22ba43c7ff2a 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -2665,6 +2665,10 @@ RISCVCPUImpliedExtsRule *riscv_multi_ext_implied_rules[] 
= {
     NULL
 };
 
+RISCVCPUPreferredExtsRule *riscv_multi_ext_preferred_rules[] = {
+    NULL
+};
+
 static Property riscv_cpu_properties[] = {
     DEFINE_PROP_BOOL("debug", RISCVCPU, cfg.debug, true),
 
diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index af25550a4a54..d775866344f5 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -142,10 +142,27 @@ typedef struct riscv_cpu_implied_exts_rule {
     const uint32_t implied_multi_exts[];
 } RISCVCPUImpliedExtsRule;
 
+typedef struct riscv_cpu_preferred_exts_rule {
+#ifndef CONFIG_USER_ONLY
+    /*
+     * Bitmask indicates the rule enabled status for the harts.
+     * This enhancement is only available in system-mode QEMU,
+     * as we don't have a good way (e.g. mhartid) to distinguish
+     * the SMP cores in user-mode QEMU.
+     */
+    unsigned long *enabled;
+#endif
+    /* multi extension offset. */
+    const uint32_t ext;
+    const uint32_t preferred_multi_exts[];
+} RISCVCPUPreferredExtsRule;
+
 extern RISCVCPUImpliedExtsRule *riscv_misa_ext_implied_rules[];
 extern RISCVCPUImpliedExtsRule *riscv_multi_ext_implied_rules[];
+extern RISCVCPUPreferredExtsRule *riscv_multi_ext_preferred_rules[];
 
 #define RISCV_IMPLIED_EXTS_RULE_END -1
+#define RISCV_PREFRRED_EXTS_RULE_END RISCV_IMPLIED_EXTS_RULE_END
 
 #define MMU_USER_IDX 3
 
diff --git a/target/riscv/tcg/tcg-cpu.c b/target/riscv/tcg/tcg-cpu.c
index 1c9a87029423..d8f74720815a 100644
--- a/target/riscv/tcg/tcg-cpu.c
+++ b/target/riscv/tcg/tcg-cpu.c
@@ -32,6 +32,7 @@
 #include "hw/core/accel-cpu.h"
 #include "hw/core/tcg-cpu-ops.h"
 #include "tcg/tcg.h"
+#include <stdio.h>
 #ifndef CONFIG_USER_ONLY
 #include "hw/boards.h"
 #endif
@@ -733,6 +734,7 @@ static void riscv_cpu_validate_profiles(RISCVCPU *cpu)
 static void riscv_cpu_init_ext_rules(void)
 {
     RISCVCPUImpliedExtsRule *rule;
+    RISCVCPUPreferredExtsRule *prule;
 #ifndef CONFIG_USER_ONLY
     MachineState *ms = MACHINE(qdev_get_machine());
 #endif
@@ -760,22 +762,40 @@ static void riscv_cpu_init_ext_rules(void)
                             GUINT_TO_POINTER(rule->ext), (gpointer)rule);
     }
 
+    for (i = 0; (prule = riscv_multi_ext_preferred_rules[i]); i++) {
+#ifndef CONFIG_USER_ONLY
+        prule->enabled = bitmap_new(ms->smp.cpus);
+#endif
+        g_hash_table_insert(multi_ext_enabling_rules,
+                            GUINT_TO_POINTER(prule->ext), (gpointer)prule);
+    }
+
     initialized = true;
 }
 
 static void cpu_enable_ext_rule(RISCVCPU *cpu,
-                                    RISCVCPUImpliedExtsRule *rule)
+                                RISCVCPUImpliedExtsRule *rule,
+                                RISCVCPUPreferredExtsRule *prule)
 {
     CPURISCVState *env = &cpu->env;
     RISCVCPUImpliedExtsRule *ir;
+    RISCVCPUPreferredExtsRule *pr;
     bool enabled = false;
     int i;
 
 #ifndef CONFIG_USER_ONLY
-    enabled = test_bit(cpu->env.mhartid, rule->enabled);
+    if (rule) {
+        enabled = test_bit(cpu->env.mhartid, rule->enabled);
+    } else if (prule) {
+        enabled = test_bit(cpu->env.mhartid, prule->enabled);
+    } else {
+        return;
+    }
 #endif
+    if (enabled)
+        return;
 
-    if (!enabled) {
+    if (rule) {
         /* Enable the implied MISAs. */
         if (rule->implied_misa_exts) {
             riscv_cpu_set_misa_ext(env,
@@ -787,7 +807,7 @@ static void cpu_enable_ext_rule(RISCVCPU *cpu,
                                              GUINT_TO_POINTER(misa_bits[i]));
 
                     if (ir) {
-                        cpu_enable_ext_rule(cpu, ir);
+                        cpu_enable_ext_rule(cpu, ir, NULL);
                     }
                 }
             }
@@ -803,12 +823,27 @@ static void cpu_enable_ext_rule(RISCVCPU *cpu,
                                             rule->implied_multi_exts[i]));
 
             if (ir) {
-                cpu_enable_ext_rule(cpu, ir);
+                cpu_enable_ext_rule(cpu, ir, NULL);
             }
         }
 
 #ifndef CONFIG_USER_ONLY
         bitmap_set(rule->enabled, cpu->env.mhartid, 1);
+#endif
+    } else if (prule) {
+        /* Enable the preferred extensions. */
+        for (i = 0;
+          prule->preferred_multi_exts[i] != RISCV_PREFRRED_EXTS_RULE_END; i++) 
{
+            cpu_cfg_ext_auto_update(cpu, prule->preferred_multi_exts[i], true);
+            pr = g_hash_table_lookup(multi_ext_enabling_rules,
+                                     GUINT_TO_POINTER(
+                                     prule->preferred_multi_exts[i]));
+            if (pr) {
+                cpu_enable_ext_rule(cpu, NULL, prule);
+            }
+        }
+#ifndef CONFIG_USER_ONLY
+        bitmap_set(prule->enabled, cpu->env.mhartid, 1);
 #endif
     }
 }
@@ -847,6 +882,7 @@ static void cpu_enable_zc_implied_rules(RISCVCPU *cpu)
 static void riscv_cpu_enable_ext_rules(RISCVCPU *cpu)
 {
     RISCVCPUImpliedExtsRule *rule;
+    RISCVCPUPreferredExtsRule *prule;
     int i;
 
     /* Enable the implied extensions for Zc. */
@@ -855,14 +891,21 @@ static void riscv_cpu_enable_ext_rules(RISCVCPU *cpu)
     /* Enable the implied MISAs. */
     for (i = 0; (rule = riscv_misa_ext_implied_rules[i]); i++) {
         if (riscv_has_ext(&cpu->env, rule->ext)) {
-            cpu_enable_ext_rule(cpu, rule);
+            cpu_enable_ext_rule(cpu, rule, NULL);
         }
     }
 
     /* Enable the implied extensions. */
     for (i = 0; (rule = riscv_multi_ext_implied_rules[i]); i++) {
         if (isa_ext_is_enabled(cpu, rule->ext)) {
-            cpu_enable_ext_rule(cpu, rule);
+            cpu_enable_ext_rule(cpu, rule, NULL);
+        }
+    }
+
+    /* Enable the preferred extensions. */
+    for (i = 0; (prule = riscv_multi_ext_preferred_rules[i]); i++) {
+        if (isa_ext_is_enabled(cpu, prule->ext)) {
+            cpu_enable_ext_rule(cpu, NULL, prule);
         }
     }
 }

-- 
2.34.1