Re: [Qemu-devel] [Qemu-ppc] [PATCH 4/4] ppc: remove excessive logging

[Alex Bennée]

Joakim Tjernlund writes:

> Alexander Graf <address@hidden> wrote on 2014/07/12 02:39:21:
>> 
>> 
>> On 11.07.14 20:22, Peter Maydell wrote:
>> > On 11 July 2014 19:15, Joakim Tjernlund 
> <address@hidden> wrote:
>> >> Peter Maydell <address@hidden> wrote on 2014/07/11 
> 19:14:25:
>> >>> On 11 July 2014 16:18, Joakim Tjernlund 
> <address@hidden>
>> >> wrote:
>> >>>> ppc logs every type of Invalid instruction. This generates a lot
>> >>> Rather than just deleting this EXCP_DUMP, I would suggest
>> >>> changing the EXCP_DUMP macro so  it only does anything
>> >>> if the user has passed the "-d int" debug logging flag:
>> >> I don't think ppc wants that. They want unconditionally
>> >> debug on to get relevant bug reports. This one is getting in the
>> >> way of normal operations so I think it should be deleted.
>> > If the PPC maintainers want that behaviour then they need
>> > to defend it. No other architecture's linux-user code spews
>> > junk to stderr for exceptions, and PPC shouldn't either.
>> > The debug log switches are exactly for allowing us to
>> > say "please turn on debug logging" when bugs are reported,
>> > and those are what we should use.
>> 
>> I agree - and it's how we behave in system emulation mode already :).
>> 
>> What do the other platforms do on illegal instructions during user mode? 
>
>> Any way we can get consistency across the board?
>
> In this case it is not an illegal insn, it is a valid insn but not just
> for the QEMU emulated CPU.

On aarch64 we do:

#define unsupported_encoding(s, insn)                                    \
    do {                                                                 \
        qemu_log_mask(LOG_UNIMP,                                         \
                      "%s:%d: unsupported instruction encoding 0x%08x "  \
                      "at pc=%016" PRIx64 "\n",                          \
                      __FILE__, __LINE__, insn, s->pc - 4);              \
        unallocated_encoding(s);                                         \
    } while (0);

So we signal it's unimplemented before falling through to the signal
generating code.

-- 
Alex Bennée