Re: [Qemu-devel] [PATCH 3/3] target-mips: Misaligned Memory Accesses for MSA

[Yongbok Kim <yongbok.kim@imgtec.com>]

On 01/05/2015 16:43, Peter Maydell wrote:
> On 1 May 2015 at 16:24, Yongbok Kim <yongbok.kim@imgtec.com> wrote:
>> MIPS SIMD Architecture vector loads and stores require misalignment support.
>> MSA Memory access should work as an atomic operation. Therefore, it has to
>> check validity of all the addresses for the operation.
>>
>> Signed-off-by: Yongbok Kim <yongbok.kim@imgtec.com>
>> ---
>>  target-mips/op_helper.c |   30 ++++++++++++++++++++++++++++++
>>  1 files changed, 30 insertions(+), 0 deletions(-)
>>
>> diff --git a/target-mips/op_helper.c b/target-mips/op_helper.c
>> index dacc92b..89a7de6 100644
>> --- a/target-mips/op_helper.c
>> +++ b/target-mips/op_helper.c
>> @@ -3571,6 +3571,24 @@ FOP_CONDN_S(sne,  (float32_lt(fst1, fst0, &env->active_fpu.fp_status)
>>  /* Element-by-element access macros */
>>  #define DF_ELEMENTS(df) (MSA_WRLEN / DF_BITS(df))
>>
>> +#if !defined(CONFIG_USER_ONLY)
>> +static bool cpu_mips_validate_msa_block_access(CPUMIPSState *env,
>> +                                        target_ulong address, int df, int rw)
>> +{
>> +    int i;
>> +    for (i = 0; i < DF_ELEMENTS(df); i++) {
>> +        if (!cpu_mips_validate_access(env, address + (i << df),
>> +            address, (1 << df), rw)) {
>> +            CPUState *cs = CPU(mips_env_get_cpu(env));
>> +            helper_raise_exception_err(env, cs->exception_index,
>> +                                       env->error_code);
> I was wondering if this would get the correct PC in the exception
> case, but we always call save_cpu_state() before calling the
> msa_ld/st_df helpers, so it will.
>
> -- PMM
Yes it does because of the save_cpu_state(). Actually I have considered to use
cpu_restore_state() with GETRA() but it looks like using save_cpu_state() is quite
common in the target-mips. It would be good such clean-up for all the cases in the future work.
But this patch I would follow existing style for the consistency.

Regards,
Yongbok