[PATCH] target/riscv: use SXL instead of MXL for read_sstatus

[Abhigyan Kumar <314abh@gmail.com>]

According to the RISC-V spec, a 64-bit system can have M-mode in 64-bit
with S-mode being 32-bit (SXL bits or mstatus[35:34] being 1). In this
case, read_sstatus should use SXL.

QEMU doesn't allow changing the SXL bits in mstatus in M-mode. This was
because of the missing MSTATUS64_SXL mask in write_mstatus. Now, both
the SXL field in mstatus can be safely modified in M-mode and
read_sstatus correctly uses SXL not MXL.

Signed-off-by: Abhigyan Kumar <314abh@gmail.com>
---
 target/riscv/tcg/csr.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/target/riscv/tcg/csr.c b/target/riscv/tcg/csr.c
index 36f2004bc..b67a5a301 100644
--- a/target/riscv/tcg/csr.c
+++ b/target/riscv/tcg/csr.c
@@ -2067,6 +2067,11 @@ static RISCVException write_mstatus(CPURISCVState *env, int csrno,
     }
 
     if (xl != MXL_RV32 || env->debugger) {
+        if ((val & MSTATUS64_SXL) != 0) {
+            mask |= MSTATUS64_SXL;
+            val = riscv_write_uxl(env, val, MSTATUS64_SXL);
+        }
+    
         if ((val & MSTATUS64_UXL) != 0) {
             mask |= MSTATUS64_UXL;
             val = riscv_write_uxl(env, val, MSTATUS64_UXL);
@@ -4014,8 +4019,8 @@ static RISCVException read_sstatus(CPURISCVState *env, int csrno,
     if (riscv_cpu_cfg(env)->ext_ssdbltrp) {
         mask |= SSTATUS_SDT;
     }
-    /* TODO: Use SXL not MXL. */
-    *val = add_status_sd(riscv_cpu_mxl(env), env->mstatus & mask);
+
+    *val = add_status_sd(riscv_cpu_sxl(env), env->mstatus & mask);
     return RISCV_EXCP_NONE;
 }
 
-- 
2.55.0