On 1/14/20 8:28 PM, Alistair Francis wrote:
> On Wed, Jan 15, 2020 at 4:18 PM <shihpo.h...@sifive.com> wrote:
>>
>> 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.hender...@linaro.org>
>> Signed-off-by: ShihPo Hung <shihpo.h...@sifive.com>
>> Reviewed-by: Richard Henderson <richard.hender...@linaro.org>
>> ---
>> target/riscv/cpu.h | 5 +----
>> 1 file changed, 1 insertion(+), 4 deletions(-)
>>
>> diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
>> index e59343e..de0a8d8 100644
>> --- a/target/riscv/cpu.h
>> +++ b/target/riscv/cpu.h
>> @@ -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);
>
> I don't think this is right, you should use the riscv_cpu_fp_enabled()
> function.
>
> Right now it's the same as env->mstatus & MSTATUS_FS but when the
> Hypervisor extension goes in riscv_cpu_fp_enabled() will be more
> complex.
Hmm. Are you sure something like
flags |= riscv_cpu_effective_mstatus(env) & MSTATUS_FS;
wouldn't be more appropriate for the hypervisor extension?
I guess I should have another browse through your hv patchset, but I worry now
about bare uses of env->mstatus, if they no longer mean what they appear to
mean.
r~
