[Qemu-devel] cpu_x86() ?

[Qemu-devel] cpu_x86() ?

[Jun Koi]

hi,

the way cpu_exec() is defined is really confused to me.

in cpu-exec.c, we define cpu_exec() function.

however, each architecture seems to redefine cpu_exec(), like we have
in target-i386/cpu.h

#define cpu_exec cpu_x86_exec

so which cpu_exec() is executed in case of tcg/x86?

also, i cannot find the definition of cpu_x86_exec() anywhere.

somebody please help?

thanks,
Jun

Re: [Qemu-devel] cpu_x86() ?

[Max Filippov]

> the way cpu_exec() is defined is really confused to me.
>
> in cpu-exec.c, we define cpu_exec() function.
>
> however, each architecture seems to redefine cpu_exec(), like we have
> in target-i386/cpu.h
>
> #define cpu_exec cpu_x86_exec
>
> so which cpu_exec() is executed in case of tcg/x86?
>
> also, i cannot find the definition of cpu_x86_exec() anywhere.

cpu_exec definition in cpu-exec.c takes place after #include "cpu.h"
which contains #define cpu_exec whatever.
In case of x86 cpu_x86_exec is actually defined by the cpu-exec.c.

-- 
Thanks.
-- Max

Re: [Qemu-devel] cpu_x86() ?

[Jun Koi]

On Tue, Nov 1, 2011 at 6:58 PM, Max Filippov <jcmvbkbc@gmail.com> wrote:
>> the way cpu_exec() is defined is really confused to me.
>>
>> in cpu-exec.c, we define cpu_exec() function.
>>
>> however, each architecture seems to redefine cpu_exec(), like we have
>> in target-i386/cpu.h
>>
>> #define cpu_exec cpu_x86_exec
>>
>> so which cpu_exec() is executed in case of tcg/x86?
>>
>> also, i cannot find the definition of cpu_x86_exec() anywhere.
>
> cpu_exec definition in cpu-exec.c takes place after #include "cpu.h"
> which contains #define cpu_exec whatever.
> In case of x86 cpu_x86_exec is actually defined by the cpu-exec.c.
>

ok, so which means cpu_exec is redefined accordingly to each architecture.

why do we need to do this weird thing? as there is no namespace
collision it seems between architectures, why dont we just let
cpu_exec() be cpu_exec()?

is this a trick? i cannot figure out why.

thanks,
Jun

Re: [Qemu-devel] cpu_x86() ?

[Andreas Färber]

Am 01.11.2011 15:34, schrieb Jun Koi:
> On Tue, Nov 1, 2011 at 6:58 PM, Max Filippov <jcmvbkbc@gmail.com> wrote:
>>> the way cpu_exec() is defined is really confused to me.
>>>
>>> in cpu-exec.c, we define cpu_exec() function.
>>>
>>> however, each architecture seems to redefine cpu_exec(), like we have
>>> in target-i386/cpu.h
>>>
>>> #define cpu_exec cpu_x86_exec
>>>
>>> so which cpu_exec() is executed in case of tcg/x86?
>>>
>>> also, i cannot find the definition of cpu_x86_exec() anywhere.
>>
>> cpu_exec definition in cpu-exec.c takes place after #include "cpu.h"
>> which contains #define cpu_exec whatever.
>> In case of x86 cpu_x86_exec is actually defined by the cpu-exec.c.
>>
> 
> ok, so which means cpu_exec is redefined accordingly to each architecture.
> 
> why do we need to do this weird thing? as there is no namespace
> collision it seems between architectures, why dont we just let
> cpu_exec() be cpu_exec()?

See the recent discussion about heterogeneous system emulation.
Such redefinitions are a handy way to avoid name collisions across
architectures.

Andreas

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Re: [Qemu-devel] cpu_x86() ?

[Max Filippov]

> > cpu_exec definition in cpu-exec.c takes place after #include "cpu.h"
> > which contains #define cpu_exec whatever.
> > In case of x86 cpu_x86_exec is actually defined by the cpu-exec.c.
> >
> 
> ok, so which means cpu_exec is redefined accordingly to each architecture.
> 
> why do we need to do this weird thing? as there is no namespace
> collision it seems between architectures, why dont we just let
> cpu_exec() be cpu_exec()?
> 
> is this a trick? i cannot figure out why.

One theory about it is the following (quoted from http://lists.nongnu.org/archive/html/qemu-devel/2011-05/msg02921.html):

One of the long standing goals for QEMU has been to be able to use a
single executable to emulate multiple architectures. I think for
example the lines like
#define cpu_init cpu_sparc_init
#define cpu_exec cpu_sparc_exec
etc. stand for this purpose, so there has been some consideration for this.

Thanks.
-- Max