Re: illegal hardware instruction during MIPS-I ELF linux useremulation

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 9/26/19 4:31 PM, Libo Zhou wrote:
>> If you look at the mips_defs[] array in
>> target/mips/translate_init.inc.c, the older ISA implemented is MIPS-II:
> 
>> $ git grep .insn_flags target/mips/translate_init.inc.c
>> translate_init.inc.c:75:        .insn_flags = CPU_MIPS32,
>> translate_init.inc.c:97:        .insn_flags = CPU_MIPS32 | ASE_MIPS16,
>> translate_init.inc.c:117:        .insn_flags = CPU_MIPS32,
>> translate_init.inc.c:137:        .insn_flags = CPU_MIPS32 | ASE_MIPS16,
>> translate_init.inc.c:158:        .insn_flags = CPU_MIPS32R2,
>> translate_init.inc.c:179:        .insn_flags = CPU_MIPS32R2 | ASE_MIPS16,
>> translate_init.inc.c:201:        .insn_flags = CPU_MIPS32R2 | ASE_MIPS16,
>> translate_init.inc.c:223:        .insn_flags = CPU_MIPS32R2 | ASE_MIPS16 | ASE_DSP,
>> translate_init.inc.c:249:        .insn_flags = CPU_MIPS32R2 | ASE_MIPS16,
>> translate_init.inc.c:297:        .insn_flags = CPU_MIPS32R2 | ASE_MIPS16 | ASE_DSP | ASE_MT,
>> translate_init.inc.c:323:        .insn_flags = CPU_MIPS32R2 | ASE_MIPS16 | ASE_DSP | ASE_DSP_R2,
>> translate_init.inc.c:343:        .insn_flags = CPU_MIPS32R2 | ASE_MICROMIPS,
>> translate_init.inc.c:364:        .insn_flags = CPU_MIPS32R2 | ASE_MICROMIPS,
>> translate_init.inc.c:410:        .insn_flags = CPU_MIPS32R5 | ASE_MSA,
>> translate_init.inc.c:449:        .insn_flags = CPU_MIPS32R6 | ASE_MICROMIPS,
>> translate_init.inc.c:488:        .insn_flags = CPU_NANOMIPS32 | ASE_DSP | ASE_DSP_R2 | ASE_DSP_R3 |
>> translate_init.inc.c:511:        .insn_flags = CPU_MIPS3,
>> translate_init.inc.c:531:        .insn_flags = CPU_VR54XX,
>> translate_init.inc.c:552:        .insn_flags = CPU_MIPS64,
>> translate_init.inc.c:578:        .insn_flags = CPU_MIPS64,
>> translate_init.inc.c:607:        .insn_flags = CPU_MIPS64 | ASE_MIPS3D,
>> translate_init.inc.c:636:        .insn_flags = CPU_MIPS64R2 | ASE_MIPS3D,
>> translate_init.inc.c:657:        .insn_flags = CPU_MIPS64R2,
>> translate_init.inc.c:681:        .insn_flags = CPU_MIPS64R2,
>> translate_init.inc.c:721:        .insn_flags = CPU_MIPS64R6 | ASE_MSA,
>> translate_init.inc.c:761:        .insn_flags = CPU_MIPS64R6 | ASE_MSA,
>> translate_init.inc.c:781:        .insn_flags = CPU_LOONGSON2E,
>> translate_init.inc.c:801:        .insn_flags = CPU_LOONGSON2F,
>> translate_init.inc.c:830:        .insn_flags = CPU_MIPS64R2 | ASE_DSP | ASE_DSP_R2,
> 
>> So currently there is no MIPS-I only CPU.
>> Note that the code got written with MIPS32 in mind, and implementing
>> MIPS-I requires a considerable amount of change in the codebase.
> 
> Hi Philippe,
> 
> I just figured out what the problem was. The custom compiler I used just modified the opcode fields of sw and lw instructions of MIPS, so QEMU didn't recognize them out of the box.
> I just added the support in decode_opc function in translate.c, and I also added my own CPU model in translate_init.inc.c. However, the illegal instruction exception is still there.
> 
> I am suspecting that the way I added my own CPU model in translate_init.inc.c is wrong. Below is what I added:
> ...
> +{
> +    .name = "MyCPU",
> +    .insn_flags = CPU_MIPS1 | INSN_MYCPU,
> +},
> ...
> I just need to simulate it's instruction set in linux user emulation, I didn't include CP0* items in the list. Is this good enough to add a new CPU model?

Something like that might be acceptable for linux-user.
You should at least set CP0_PRid/Config0/Status_mask.

Look at this patch where Aleksandar accepted the R5900 CPU:
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=ed4f49ba9bb56

Can you share what is your CPU?