[PATCH v2 1/3] target/riscv: Fix tb->flags FS status

[shihpo.hung@sifive.com]

It was found that running libquantum on riscv-linux qemu produced an
incorrect result. After investigation, FP registers are not saved
during context switch due to incorrect mstatus.FS.

In current implementation tb->flags merges all non-disabled state to
dirty. This means the code in mark_fs_dirty in translate.c that
handles initial and clean states is unreachable.

This patch fixes it and is successfully tested with:
  libquantum

Thanks to Richard for pointing out the actual bug.

Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: ShihPo Hung <shihpo.hung@sifive.com>
---
 target/riscv/cpu.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index e59343e..f0ff57e 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -295,7 +295,7 @@ static inline void cpu_get_tb_cpu_state(CPURISCVState *env, target_ulong *pc,
 #else
     *flags = cpu_mmu_index(env, 0);
     if (riscv_cpu_fp_enabled(env)) {
-        *flags |= TB_FLAGS_MSTATUS_FS;
+        *flags |= env->mstatus & MSTATUS_FS;
     }
 #endif
 }
-- 
2.7.4