Re: [Xen-devel] [PATCH 1/2] x86: during boot, anticipate identifying the boot cpu

[George Dunlap <george.dunlap@xxxxxxxxxxxxx>]

On 08/25/2014 09:39 AM, Jan Beulich wrote:
> > > > On 22.08.14 at 19:15, <dario.faggioli@xxxxxxxxxx> wrote:
> > --- a/xen/arch/x86/setup.c
> > +++ b/xen/arch/x86/setup.c
> > @@ -1262,6 +1262,12 @@ void __init noreturn __start_xen(unsigned long mbi_p)
> >   
> >       timer_init();
> >   
> > +    /*
> > +     * Identify the boot CPU, in case the scheduler initialization
> > +     * needs to know about it (e.g., topology, etc.)
> > +     */
> > +    identify_cpu(&boot_cpu_data);
> > +
> >       init_idle_domain();
> >   
> >       trap_init();
> > @@ -1272,8 +1278,6 @@ void __init noreturn __start_xen(unsigned long mbi_p)
> >   
> >       arch_init_memory();
> >   
> > -    identify_cpu(&boot_cpu_data);
> > -
> >       if ( cpu_has_fxsr )
> >           set_in_cr4(X86_CR4_OSFXSR);
> >       if ( cpu_has_xmm )
> I'm not sure about this part: It currently makes quite a bit of sense
> to have identify_cpu() immediately before explicit users of the
> gathered data (all code following up to the alternative_instructions()
> call). Perhaps if you move identify_cpu(), all the others should get
> moved too?
Or possibly, move init_idle_domain() until after?  I took a quick look 
through the functions called between init_idle_domain() and 
identify_cpu(), and didn't see any dependencies on the idle domain or 
scheduling functions.  It's quite possible I missed something though.
Overall I think this approach looks good, and I agree with the comments 
already given.
 -George

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