linux-kernel - Re: [PATCH 23/25] [PATCH] paravirt hooks for arch initialization

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Date:	Wed, 8 Aug 2007 11:08:25 -0300
From:	"Glauber de Oliveira Costa" <glommer@...il.com>
To:	"Andi Kleen" <ak@...e.de>
Cc:	"Glauber de Oliveira Costa" <gcosta@...hat.com>,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	rusty@...tcorp.com.au, mingo@...e.hu, chrisw@...s-sol.org,
	jeremy@...p.org, avi@...ranet.com, anthony@...emonkey.ws,
	virtualization@...ts.linux-foundation.org, lguest@...abs.org,
	"Steven Rostedt" <rostedt@...dmis.org>
Subject: Re: [PATCH 23/25] [PATCH] paravirt hooks for arch initialization

On 8/8/07, Andi Kleen <ak@...e.de> wrote:
>
> > -static void discover_ebda(void)
> > +void native_ebda_info(unsigned *addr, unsigned *size)
>
> I guess it would be better to use the resources frame work here.
> Before checking EBDA check if it is already reserved. Then lguest/Xen
> can reserve these areas and stop using it.
Let's make sure I understand: So you suggest skipping discover
altogether in case it is already reserved?

>
> > +/* Overridden in paravirt.c if CONFIG_PARAVIRT */
> > +void __attribute__((weak)) memory_setup(void)
> > +{
> > +       return setup_memory_region();
> > +}
> > +
> > +
> >  void __init setup_arch(char **cmdline_p)
> >  {
> >       printk(KERN_INFO "Command line: %s\n", boot_command_line);
> > @@ -231,12 +255,19 @@ void __init setup_arch(char **cmdline_p)
> >       saved_video_mode = SAVED_VIDEO_MODE;
> >       bootloader_type = LOADER_TYPE;
> >
> > +     /*
> > +      * By returning non-zero here, a paravirt impl can choose to
> > +      * skip the rest of the setup process
> > +      */
> > +     if (paravirt_arch_setup())
> > +             return;
>
> Sorry, but that's an extremly ugly and clumpsy interface and will lead
> to extensive code duplication in hypervisors because so much code
> is disabled.

We can just wipe out the return value right now. Note that it was a
choice, it would only lead to code duplication if the hypervisor
wanted it. But yeah, I understand your concern. They may chose to
return 1 here just to change some tiny thing in the bottom.

I don't know exactly what other kinds of hooks we could put there.
lguest surely didn't need any. Are you okay with just turning it into
void by now ?

-- 
Glauber de Oliveira Costa.
"Free as in Freedom"
http://glommer.net

"The less confident you are, the more serious you have to act."
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