target/riscv: Add Smrnmi CSRs

The Smrnmi extension adds the 'mnscratch', 'mnepc', 'mncause',
'mnstatus' CSRs.

Signed-off-by: Frank Chang <frank.chang@sifive.com>
Signed-off-by: Tommy Wu <tommy.wu@sifive.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20250106054336.1878291-3-frank.chang@sifive.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

4 files changed, 105 insertions, 0 deletions

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index d9eb2c0..66193cd 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -1127,6 +1127,11 @@ static void riscv_cpu_reset_hold(Object *obj, ResetType type)
         riscv_trigger_reset_hold(env);
     }
 
+    if (cpu->cfg.ext_smrnmi) {
+        env->rnmip = 0;
+        env->mnstatus = set_field(env->mnstatus, MNSTATUS_NMIE, false);
+    }
+
     if (kvm_enabled()) {
         kvm_riscv_reset_vcpu(cpu);
     }
diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index 5e71522..5eaf9da 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -480,6 +480,13 @@ struct CPUArchState {
     uint64_t kvm_timer_state;
     uint64_t kvm_timer_frequency;
 #endif /* CONFIG_KVM */
+
+    /* RNMI */
+    target_ulong mnscratch;
+    target_ulong mnepc;
+    target_ulong mncause; /* mncause without bit XLEN-1 set to 1 */
+    target_ulong mnstatus;
+    target_ulong rnmip;
 };
 
 /*
diff --git a/target/riscv/cpu_bits.h b/target/riscv/cpu_bits.h
index 797dd69..ba6fc54 100644
--- a/target/riscv/cpu_bits.h
+++ b/target/riscv/cpu_bits.h
@@ -353,6 +353,12 @@
 #define CSR_PMPADDR14       0x3be
 #define CSR_PMPADDR15       0x3bf
 
+/* RNMI */
+#define CSR_MNSCRATCH       0x740
+#define CSR_MNEPC           0x741
+#define CSR_MNCAUSE         0x742
+#define CSR_MNSTATUS        0x744
+
 /* Debug/Trace Registers (shared with Debug Mode) */
 #define CSR_TSELECT         0x7a0
 #define CSR_TDATA1          0x7a1
@@ -604,6 +610,11 @@ typedef enum {
 #define SATP64_ASID         0x0FFFF00000000000ULL
 #define SATP64_PPN          0x00000FFFFFFFFFFFULL
 
+/* RNMI mnstatus CSR mask */
+#define MNSTATUS_NMIE       0x00000008
+#define MNSTATUS_MNPV       0x00000080
+#define MNSTATUS_MNPP       0x00001800
+
 /* VM modes (satp.mode) privileged ISA 1.10 */
 #define VM_1_10_MBARE       0
 #define VM_1_10_SV32        1
diff --git a/target/riscv/csr.c b/target/riscv/csr.c
index 6b8cef5..af97667 100644
--- a/target/riscv/csr.c
+++ b/target/riscv/csr.c
@@ -590,6 +590,17 @@ static RISCVException debug(CPURISCVState *env, int csrno)
 
     return RISCV_EXCP_ILLEGAL_INST;
 }
+
+static RISCVException rnmi(CPURISCVState *env, int csrno)
+{
+    RISCVCPU *cpu = env_archcpu(env);
+
+    if (cpu->cfg.ext_smrnmi) {
+        return RISCV_EXCP_NONE;
+    }
+
+    return RISCV_EXCP_ILLEGAL_INST;
+}
 #endif
 
 static RISCVException seed(CPURISCVState *env, int csrno)
@@ -4376,6 +4387,67 @@ static RISCVException write_mcontext(CPURISCVState *env, int csrno,
     return RISCV_EXCP_NONE;
 }
 
+static RISCVException read_mnscratch(CPURISCVState *env, int csrno,
+                                     target_ulong *val)
+{
+    *val = env->mnscratch;
+    return RISCV_EXCP_NONE;
+}
+
+static int write_mnscratch(CPURISCVState *env, int csrno, target_ulong val)
+{
+    env->mnscratch = val;
+    return RISCV_EXCP_NONE;
+}
+
+static int read_mnepc(CPURISCVState *env, int csrno, target_ulong *val)
+{
+    *val = env->mnepc;
+    return RISCV_EXCP_NONE;
+}
+
+static int write_mnepc(CPURISCVState *env, int csrno, target_ulong val)
+{
+    env->mnepc = val;
+    return RISCV_EXCP_NONE;
+}
+
+static int read_mncause(CPURISCVState *env, int csrno, target_ulong *val)
+{
+    *val = env->mncause;
+    return RISCV_EXCP_NONE;
+}
+
+static int write_mncause(CPURISCVState *env, int csrno, target_ulong val)
+{
+    env->mncause = val;
+    return RISCV_EXCP_NONE;
+}
+
+static int read_mnstatus(CPURISCVState *env, int csrno, target_ulong *val)
+{
+    *val = env->mnstatus;
+    return RISCV_EXCP_NONE;
+}
+
+static int write_mnstatus(CPURISCVState *env, int csrno, target_ulong val)
+{
+    target_ulong mask = (MNSTATUS_NMIE | MNSTATUS_MNPP);
+
+    if (riscv_has_ext(env, RVH)) {
+        /* Flush tlb on mnstatus fields that affect VM. */
+        if ((val ^ env->mnstatus) & MNSTATUS_MNPV) {
+            tlb_flush(env_cpu(env));
+        }
+
+        mask |= MNSTATUS_MNPV;
+    }
+
+    /* mnstatus.mnie can only be cleared by hardware. */
+    env->mnstatus = (env->mnstatus & MNSTATUS_NMIE) | (val & mask);
+    return RISCV_EXCP_NONE;
+}
+
 #endif
 
 /* Crypto Extension */
@@ -4883,6 +4955,16 @@ riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
                         write_sstateen_1_3,
                         .min_priv_ver = PRIV_VERSION_1_12_0 },
 
+    /* RNMI */
+    [CSR_MNSCRATCH] = { "mnscratch", rnmi, read_mnscratch, write_mnscratch,
+                        .min_priv_ver = PRIV_VERSION_1_12_0               },
+    [CSR_MNEPC]     = { "mnepc",     rnmi, read_mnepc,     write_mnepc,
+                        .min_priv_ver = PRIV_VERSION_1_12_0               },
+    [CSR_MNCAUSE]   = { "mncause",   rnmi, read_mncause,   write_mncause,
+                        .min_priv_ver = PRIV_VERSION_1_12_0               },
+    [CSR_MNSTATUS]  = { "mnstatus",  rnmi, read_mnstatus,  write_mnstatus,
+                        .min_priv_ver = PRIV_VERSION_1_12_0               },
+
     /* Supervisor Trap Setup */
     [CSR_SSTATUS]    = { "sstatus",    smode, read_sstatus,    write_sstatus,
                          NULL,                read_sstatus_i128              },