[RFC PATCH 1/4] target/riscv: smstateen check for fcsr

[Mayuresh Chitale]

If smstateen is implemented and sstateen0.fcsr is clear then the
floating point operations must return illegal instruction exception
or virtual instruction trap, if relevant.

Signed-off-by: Mayuresh Chitale <mchitale@ventanamicro.com>
---
 target/riscv/cpu.h |  3 +++
 target/riscv/csr.c | 25 ++++++++++++++++++++++++-
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index 638e47c75a..132cf06ff2 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -613,6 +613,9 @@ void riscv_cpu_set_aia_ireg_rmw_fn(CPURISCVState *env, 
uint32_t priv,
                                                  target_ulong new_val,
                                                  target_ulong write_mask),
                                    void *rmw_fn_arg);
+RISCVException smstateen_acc_ok(CPURISCVState *env, int index, uint64_t bit);
+#else
+#define smstateen_acc_ok(env, index, bit) RISCV_EXCP_NONE
 #endif
 void riscv_cpu_set_mode(CPURISCVState *env, target_ulong newpriv);
 
diff --git a/target/riscv/csr.c b/target/riscv/csr.c
index d522efc0b6..4979058434 100644
--- a/target/riscv/csr.c
+++ b/target/riscv/csr.c
@@ -43,7 +43,7 @@ void riscv_set_csr_ops(int csrno, riscv_csr_operations *ops)
 
 /* Predicates */
 #if !defined(CONFIG_USER_ONLY)
-static RISCVException smstateen_acc_ok(CPURISCVState *env, int index,
+RISCVException smstateen_acc_ok(CPURISCVState *env, int index,
                                        uint64_t bit)
 {
     bool virt = riscv_cpu_virt_enabled(env);
@@ -83,6 +83,10 @@ static RISCVException fs(CPURISCVState *env, int csrno)
         !riscv_cpu_cfg(env)->ext_zfinx) {
         return RISCV_EXCP_ILLEGAL_INST;
     }
+
+    if (!env->debugger && !riscv_cpu_fp_enabled(env)) {
+        return smstateen_acc_ok(env, 0, SMSTATEEN0_FCSR);
+    }
 #endif
     return RISCV_EXCP_NONE;
 }
@@ -2056,6 +2060,9 @@ static RISCVException write_mstateen0(CPURISCVState *env, 
int csrno,
                                       target_ulong new_val)
 {
     uint64_t wr_mask = SMSTATEEN_STATEEN | SMSTATEEN0_HSENVCFG;
+    if (!riscv_has_ext(env, RVF)) {
+        wr_mask |= SMSTATEEN0_FCSR;
+    }
 
     return write_mstateen(env, csrno, wr_mask, new_val);
 }
@@ -2092,6 +2099,10 @@ static RISCVException write_mstateen0h(CPURISCVState 
*env, int csrno,
 {
     uint64_t wr_mask = SMSTATEEN_STATEEN | SMSTATEEN0_HSENVCFG;
 
+    if (!riscv_has_ext(env, RVF)) {
+        wr_mask |= SMSTATEEN0_FCSR;
+    }
+
     return write_mstateenh(env, csrno, wr_mask, new_val);
 }
 
@@ -2129,6 +2140,10 @@ static RISCVException write_hstateen0(CPURISCVState 
*env, int csrno,
 {
     uint64_t wr_mask = SMSTATEEN_STATEEN | SMSTATEEN0_HSENVCFG;
 
+    if (!riscv_has_ext(env, RVF)) {
+        wr_mask |= SMSTATEEN0_FCSR;
+    }
+
     return write_hstateen(env, csrno, wr_mask, new_val);
 }
 
@@ -2168,6 +2183,10 @@ static RISCVException write_hstateen0h(CPURISCVState 
*env, int csrno,
 {
     uint64_t wr_mask = SMSTATEEN_STATEEN | SMSTATEEN0_HSENVCFG;
 
+    if (!riscv_has_ext(env, RVF)) {
+        wr_mask |= SMSTATEEN0_FCSR;
+    }
+
     return write_hstateenh(env, csrno, wr_mask, new_val);
 }
 
@@ -2215,6 +2234,10 @@ static RISCVException write_sstateen0(CPURISCVState 
*env, int csrno,
 {
     uint64_t wr_mask = SMSTATEEN_STATEEN | SMSTATEEN0_HSENVCFG;
 
+    if (!riscv_has_ext(env, RVF)) {
+        wr_mask |= SMSTATEEN0_FCSR;
+    }
+
     return write_sstateen(env, csrno, wr_mask, new_val);
 }
 
-- 
2.34.1