Re: [Qemu-arm] [Qemu-devel] [PATCH v9 21/26] target: [tcg, arm] Port to insn_start

[Lluís Vilanova]

Richard Henderson writes:

> On 06/25/2017 03:08 AM, Lluís Vilanova wrote:
>> +static void arm_trblock_insn_start(DisasContextBase *db, CPUState *cpu)
>> +{
>> +    DisasContext *dc = container_of(db, DisasContext, base);
>> +
>> +    dc->insn_start_idx = tcg_op_buf_count();
>> +    tcg_gen_insn_start(dc->pc,
>> +                       (dc->condexec_cond << 4) | (dc->condexec_mask >> 1),
>> +                       0);
>> +
>> +#ifdef CONFIG_USER_ONLY
>> +    /* Intercept jump to the magic kernel page.  */
>> +    if (dc->pc >= 0xffff0000) {
>> +        /* We always get here via a jump, so know we are not in a
>> +           conditional execution block.  */
>> +        gen_exception_internal(EXCP_KERNEL_TRAP);
>> +        dc->is_jmp = DJ_EXC;
>> +    }
>> +#endif
>> +}

> I think this DJ_EXC block is better placed at the start of disas_insn.

> It is, however, the answer to one of my questions re patch 4/26.

It cannot, because DJ_EXC make the generic code break out of trasnlation before
doing anything else, which is what the original code does.

Cheers,
  Lluis