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From: Peter Maydell <peter.maydell@linaro.org>
Date: Tue, 4 Jul 2017 20:14:05 +0100
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Subject: Re: [Qemu-devel] [PATCH v11 04/29] target: [tcg] Add generic
 translation framework
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To: Richard Henderson <rth@twiddle.net>, QEMU Developers <qemu-devel@nongnu.org>, Paolo Bonzini <pbonzini@redhat.com>, Peter Crosthwaite <crosthwaite.peter@gmail.com>, "Emilio G. Cota" <cota@braap.org>, =?UTF-8?B?QWxleCBCZW5uw6ll?= <alex.bennee@linaro.org>

On 4 July 2017 at 19:59, Llu=C3=ADs Vilanova <vilanova@ac.upc.edu> wrote:
> Richard Henderson writes:
>
>> On 06/28/2017 05:32 AM, Llu=C3=ADs Vilanova wrote:
>>> +    void (*init_disas_context)(DisasContextBase *db, CPUState *cpu);
>>> +    void (*init_globals)(DisasContextBase *db, CPUState *cpu);
>>> +    void (*tb_start)(DisasContextBase *db, CPUState *cpu);
>>> +    void (*insn_start)(DisasContextBase *db, CPUState *cpu);
>>> +    BreakpointCheckType (*breakpoint_check)(DisasContextBase *db, CPUS=
tate *cpu,
>>> +                                            const CPUBreakpoint *bp);
>>> +    target_ulong (*translate_insn)(DisasContextBase *db, CPUState *cpu=
);
>>> +    void (*tb_stop)(DisasContextBase *db, CPUState *cpu);
>>> +    void (*disas_log)(const DisasContextBase *db, CPUState *cpu);
>
>> Any reason not to stuff the cpu pointer into the DisasContextBase instea=
d of
>> passing it around separately?
>
> None, really. I'll move it from DisasContext (in targets where it's prese=
nt)
> into DisasContextBase, and use that one everywhere.

I kind of like not having CPUState* in DisasContext, because
it enforces the rule that you can't read from fields of
it inside the target translate.c code without jumping through
a hoop (ie copying the info from CPUState->foo to
DisasContext->foo). That then acts as a useful flag in code
review (or when writing the code) to confirm that foo really
is constant for the life of the simulation (or to recommend
using a TB flag instead).

thanks
-- PMM