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target/riscv: Fix tb->flags FS status

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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.

v3: remove the redundant condition
v2: root cause FS problem

Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: ShihPo Hung <shihpo.hung@sifive.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
This commit is contained in:
ShihPo Hung 2020-01-14 22:17:31 -08:00 committed by Palmer Dabbelt
parent a37f21c27d
commit 613fa160e1
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GPG Key ID: 2E1319F35FBB1889
1 changed files with 1 additions and 4 deletions
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5
target/riscv/cpu.h
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@ -293,10 +293,7 @@ static inline void cpu_get_tb_cpu_state(CPURISCVState *env, target_ulong *pc,
#ifdef CONFIG_USER_ONLY
*flags = TB_FLAGS_MSTATUS_FS;
#else
*flags = cpu_mmu_index(env, 0);
if (riscv_cpu_fp_enabled(env)) {
*flags |= TB_FLAGS_MSTATUS_FS;
}
*flags = cpu_mmu_index(env, 0) | (env->mstatus & MSTATUS_FS);
#endif
}