Re: [Qemu-devel] [PULL 04/11] target-i386: Rename cpu_x86_init() to cpu_x86_init_user()

["Andreas Färber" <afaerber@suse.de>]

Am 27.02.2015 um 20:01 schrieb Eduardo Habkost:
> On Fri, Feb 27, 2015 at 03:10:27PM +0100, Andreas Färber wrote:
>> Am 26.02.2015 um 16:59 schrieb Eduardo Habkost:
>>> On Wed, Feb 25, 2015 at 11:06:55PM +0100, Andreas Färber wrote:
>>>> Am 25.02.2015 um 20:58 schrieb Eduardo Habkost:
>>>>> The function is used only for CONFIG_USER, so make its purpose clear.
>>>>>
>>>>> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
>>>>> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
>>>>> ---
>>>>>  target-i386/cpu.c | 2 +-
>>>>>  target-i386/cpu.h | 4 ++--
>>>>>  2 files changed, 3 insertions(+), 3 deletions(-)
>>>>
>>>> Please don't. I happily got all architectures aligned that it's at least
>>>> cpu_something_init, and it only happens to be user-only for x86. It is
>>>> rather the legacy function that was used in both system and user.
>>>
>>> If that's a legacy function, what are the steps you plan to follow to
>>> eliminate it? I would be glad to help eliminating legacy code.
>>>
>>> Initialization of CPUs in *-user and *-softmmu is different in i386, so
>>> we are going to have different code for both. How do you think I should
>>> name the *-user-specific CPU init function in target-i386, then?
>>
>> I would prefer to leave its name as it is (unless we are renaming all,
>> which would probably be a waste of effort giving the next steps) and
>> simply not use it in PC code. If you want to enforce this, you could
>> #ifdef CONFIG_USER_ONLY it.
>>
>> For some targets - as can be seen in your uc32 patch - there is already
>> a cpu_generic_init() that calls into the CPUClass hooks of the given CPU
>> type. I would like to call that from linux-user directly (or from a
>> lightweight wrapper to be shared between linux-user and bsd-user, I
>> assume we're going need some target-specific #ifdefs) and drop
>> cpu_init() in its current form. In particular I want to somehow move the
>> realized=true part out of it, which means either inlining it into dozens
>> of machines or finishing the recursive realization work so that we only
>> need one central realized=true for /machine.
> 
> Moving realized=true outside cpu_generic_init() would make lots of sense
> for PC, as we already need to perform additional steps in the PC init
> code before realizing the CPU (and I expect the list of PC-specific CPU
> initialization steps to grow). And when we do this, cpu_x86_init()
> (used by CONFIG_USER) and cpu_x86_create() (used by PC) can become the
> same function.
> 
> But I don't see how to implement this without requiring changing machine
> code case-by-case, as existing machine code may expect realized=true to
> be set very early and break if you don't set it immediately after
> cpu_*_init(). In other words, even if we implement recursive
> realization, we may need to inline realize=true on all machines as an
> intermediate (and automated) step, and then change machines to just rely
> on recursive realization, one by one.

Yes, that's why it's not done yet, it takes a lot of review and testing.
It is not going to be a pure Coccinelle patch. :) Doing that for the
inlining is an idea I had not yet considered, thanks.

On my qom-cpu-x86 branch I have already moved realized=true for the PC,
in order to make a CPU core object its parent.

Regards,
Andreas

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