[PULL 39/50] target/riscv: Fix henvcfg potentially containing stale bits

[Alistair Francis]

From: Clément Léger <cleger@rivosinc.com>

With the current implementation, if we had the following scenario:
- Set bit x in menvcfg
- Set bit x in henvcfg
- Clear bit x in menvcfg
then, the internal variable env->henvcfg would still contain bit x due
to both a wrong menvcfg mask used in write_henvcfg() as well as a
missing update of henvcfg upon menvcfg update.
This can lead to some wrong interpretation of the context. In order to
update henvcfg upon menvcfg writing, call write_henvcfg() after writing
menvcfg. Clearing henvcfg upon writing the new value is also needed in
write_henvcfg() as well as clearing henvcfg upper part when writing it
with write_henvcfgh().

Signed-off-by: Clément Léger <cleger@rivosinc.com>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20250110125441.3208676-2-cleger@rivosinc.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
---
 target/riscv/csr.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/target/riscv/csr.c b/target/riscv/csr.c
index eddcf5a5d0..279293b86d 100644
--- a/target/riscv/csr.c
+++ b/target/riscv/csr.c
@@ -2946,6 +2946,8 @@ static RISCVException read_menvcfg(CPURISCVState *env, 
int csrno,
     return RISCV_EXCP_NONE;
 }
 
+static RISCVException write_henvcfg(CPURISCVState *env, int csrno,
+                                    target_ulong val);
 static RISCVException write_menvcfg(CPURISCVState *env, int csrno,
                                     target_ulong val)
 {
@@ -2974,6 +2976,7 @@ static RISCVException write_menvcfg(CPURISCVState *env, 
int csrno,
         }
     }
     env->menvcfg = (env->menvcfg & ~mask) | (val & mask);
+    write_henvcfg(env, CSR_HENVCFG, env->henvcfg);
 
     return RISCV_EXCP_NONE;
 }
@@ -2985,6 +2988,8 @@ static RISCVException read_menvcfgh(CPURISCVState *env, 
int csrno,
     return RISCV_EXCP_NONE;
 }
 
+static RISCVException write_henvcfgh(CPURISCVState *env, int csrno,
+                                    target_ulong val);
 static RISCVException write_menvcfgh(CPURISCVState *env, int csrno,
                                      target_ulong val)
 {
@@ -2996,6 +3001,7 @@ static RISCVException write_menvcfgh(CPURISCVState *env, 
int csrno,
     uint64_t valh = (uint64_t)val << 32;
 
     env->menvcfg = (env->menvcfg & ~mask) | (valh & mask);
+    write_henvcfgh(env, CSR_HENVCFGH, env->henvcfg >> 32);
 
     return RISCV_EXCP_NONE;
 }
@@ -3101,7 +3107,7 @@ static RISCVException write_henvcfg(CPURISCVState *env, 
int csrno,
         }
     }
 
-    env->henvcfg = (env->henvcfg & ~mask) | (val & mask);
+    env->henvcfg = val & mask;
 
     return RISCV_EXCP_NONE;
 }
@@ -3134,7 +3140,7 @@ static RISCVException write_henvcfgh(CPURISCVState *env, 
int csrno,
         return ret;
     }
 
-    env->henvcfg = (env->henvcfg & ~mask) | (valh & mask);
+    env->henvcfg = (env->henvcfg & 0xFFFFFFFF) | (valh & mask);
     return RISCV_EXCP_NONE;
 }
 
-- 
2.47.1