[ RFC 2/6] target/riscv: Implement mcountinhibit CSR

[Atish Patra]

As per the privilege specification v1.11, mcountinhibit allows to start/stop
a pmu counter selectively.

Signed-off-by: Atish Patra <atish.pa...@wdc.com>
---
 target/riscv/cpu.h      |  2 ++
 target/riscv/cpu_bits.h |  4 ++++
 target/riscv/csr.c      | 23 +++++++++++++++++++++++
 target/riscv/machine.c  |  1 +
 4 files changed, 30 insertions(+)

diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index 7bee351f3c99..ef2a7fdc3980 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -214,6 +214,8 @@ struct CPURISCVState {
     target_ulong scounteren;
     target_ulong mcounteren;
 
+    target_ulong mcountinhibit;
+
     target_ulong sscratch;
     target_ulong mscratch;
 
diff --git a/target/riscv/cpu_bits.h b/target/riscv/cpu_bits.h
index b42dd4f8d8b1..7514d611cd0b 100644
--- a/target/riscv/cpu_bits.h
+++ b/target/riscv/cpu_bits.h
@@ -283,6 +283,10 @@
 #define CSR_MHPMCOUNTER29   0xb1d
 #define CSR_MHPMCOUNTER30   0xb1e
 #define CSR_MHPMCOUNTER31   0xb1f
+
+/* Machine counter-inhibit register */
+#define CSR_MCOUNTINHIBIT   0x320
+
 #define CSR_MHPMEVENT3      0x323
 #define CSR_MHPMEVENT4      0x324
 #define CSR_MHPMEVENT5      0x325
diff --git a/target/riscv/csr.c b/target/riscv/csr.c
index 7166f8d710a8..b9d795389532 100644
--- a/target/riscv/csr.c
+++ b/target/riscv/csr.c
@@ -631,6 +631,26 @@ static int write_mtvec(CPURISCVState *env, int csrno, 
target_ulong val)
     return 0;
 }
 
+static int read_mcountinhibit(CPURISCVState *env, int csrno, target_ulong *val)
+{
+    if (env->priv_ver < PRIV_VERSION_1_11_0) {
+        return -RISCV_EXCP_ILLEGAL_INST;
+    }
+
+    *val = env->mcountinhibit;
+    return 0;
+}
+
+static int write_mcountinhibit(CPURISCVState *env, int csrno, target_ulong val)
+{
+    if (env->priv_ver < PRIV_VERSION_1_11_0) {
+        return -RISCV_EXCP_ILLEGAL_INST;
+    }
+
+    env->mcountinhibit = val;
+    return 0;
+}
+
 static int read_mcounteren(CPURISCVState *env, int csrno, target_ulong *val)
 {
     *val = env->mcounteren;
@@ -1533,6 +1553,9 @@ riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
     [CSR_MHPMCOUNTER30]  = { "mhpmcounter30",  any,    read_zero },
     [CSR_MHPMCOUNTER31]  = { "mhpmcounter31",  any,    read_zero },
 
+    [CSR_MCOUNTINHIBIT]  = { "mcountinhibi",   any,    read_mcountinhibit,
+                                                       write_mcountinhibit },
+
     [CSR_MHPMEVENT3]     = { "mhpmevent3",     any,    read_zero },
     [CSR_MHPMEVENT4]     = { "mhpmevent4",     any,    read_zero },
     [CSR_MHPMEVENT5]     = { "mhpmevent5",     any,    read_zero },
diff --git a/target/riscv/machine.c b/target/riscv/machine.c
index 27fcc770aa4b..cb7ec8a4c656 100644
--- a/target/riscv/machine.c
+++ b/target/riscv/machine.c
@@ -177,6 +177,7 @@ const VMStateDescription vmstate_riscv_cpu = {
         VMSTATE_UINTTL(env.mtval, RISCVCPU),
         VMSTATE_UINTTL(env.scounteren, RISCVCPU),
         VMSTATE_UINTTL(env.mcounteren, RISCVCPU),
+        VMSTATE_UINTTL(env.mcountinhibit, RISCVCPU),
         VMSTATE_UINTTL(env.sscratch, RISCVCPU),
         VMSTATE_UINTTL(env.mscratch, RISCVCPU),
         VMSTATE_UINT64(env.mfromhost, RISCVCPU),
-- 
2.25.1