Re: [Qemu-devel] [PATCH 11/21] target-mips: Status.UX/SX/KX enable 32-bit address wrapping

[Leon Alrae <leon.alrae@imgtec.com>]

On 30/05/14 23:41, Aurelien Jarno wrote:
>> In R6 the special behaviour for data references is also specified for Kernel
>> and Supervisor mode. Therefore MIPS_HFLAG_UX is replaced by generic MIPS_HFLAG_X
>> indicating whether 64-bit mode is enabled in current operating mode.
> 
> I haven't found any indication of that in the MIPS64R6 manual (MD00091
> version 6.00). Section 4.10 still only mentions the user mode.
> 
> Did I miss something?

You can find it in the Volume-II document (MD00087): Section "2.2.2.4.3
memory_address". It seems that some parts of MD00091 document haven't
been fully updated yet.


>> +#if defined(TARGET_MIPS64)
>> +static inline int is_wrapping_needed(DisasContext *ctx)
>> +{
>> +    if (!(ctx->hflags & MIPS_HFLAG_X)) {
>> +        /* If not R6 then wrap only in User Mode */
>> +        if ((ctx->insn_flags & ISA_MIPS64R6) ||
>> +            ((ctx->hflags & MIPS_HFLAG_KSU) == MIPS_HFLAG_UM)) {
>> +            return 1;
>> +        }
>> +    }
>> +    return 0;
>> +}
>> +#endif
> 
> As Richard said, this code should be moved above, and the HFLAG semantic
> should be changed to "address wrapping needed". The current code is
> already wrong (and I am afraid I am the author...).
> 
> So this could be done by renaming the HFLAG to for exemple
> MIPS_HFLAG_AWRAP, and checking only for this flag in gen_op_addr_add.
> Then the checks have to be adapted in compute_hflags, including the R6
> case.

I'll correct this. Thanks for the suggestion.

Leon