linux-kernel - Re: [Xen-devel] [PATCH 1/2] xen: vnuma support for PV guests running as domU.

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Date:	Thu, 14 Nov 2013 09:11:20 -0500
From:	Elena Ufimtseva <ufimtseva@...il.com>
To:	Dario Faggioli <dario.faggioli@...rix.com>
Cc:	David Vrabel <david.vrabel@...rix.com>,
	Ian Campbell <ian.campbell@...rix.com>, wency@...fujitsu.com,
	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	x86@...nel.org, linux-kernel@...r.kernel.org,
	tangchen@...fujitsu.com, mingo@...hat.com, tglx@...utronix.de,
	hpa@...or.com, xen-devel@...ts.xenproject.org,
	akpm@...ux-foundation.org,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>
Subject: Re: [Xen-devel] [PATCH 1/2] xen: vnuma support for PV guests running
 as domU.

On Thu, Nov 14, 2013 at 6:48 AM, Dario Faggioli
<dario.faggioli@...rix.com> wrote:
> On gio, 2013-11-14 at 11:21 +0000, David Vrabel wrote:
>> On 14/11/13 07:26, Dario Faggioli wrote:
>> > IIRC, it's more something that was already happening (the breakage, I
>> > mean), than a "safety net" for the unforeseeable future. Might be worth
>> > giving some context about it, perhaps referencing the email thread or
>> > the git commit hash in the comment.
>>
>> Yes, a comment like:
>>
>> /*
>>  * Set a dummy node and return success.  This prevents calling any
>>  * hardware-specific initializers which do not work in a PV guest.
>>  */
>>
>> is better.  No need to refer to any specific threads.  It's pretty clear
>> that any hardware-specific init isn't appropriate for a PV guest.
>>
> Ok.
>
>> >> +  if (rc != 0) {
>> >> +          for (i = 0; i < MAX_LOCAL_APIC; i++)
>> >> +                  set_apicid_to_node(i, NUMA_NO_NODE);
>> >> +          nodes_clear(numa_nodes_parsed);
>> >> +          nodes_clear(node_possible_map);
>> >> +          nodes_clear(node_online_map);
>> >> +          node_set(0, numa_nodes_parsed);
>> >> +          numa_add_memblk(0, 0, PFN_PHYS(max_pfn));
>> >> +  }
>> >> +  return 0;
>> >>
>> > Ok, so, we always return 'success', as we were saying during last round.
>> > However, we do not call dummy_numa_init() directly, and instead we do
>> > all these stuff, with the last two statements being exactly what
>> > dummy_numa_init() does. Reason is linking, i.e., the fact that
>> > dummy_numa_init() is not exported and you can't reach it from here,
>> > right?

Ah, my bad, I left these comments and they dont make sense :)
>>
>> I think this bit is fine as-is.
>>
> Ok, cool. :-) Shouldn't we then kill or reformulate the comments where
> dummy_numa_init is explicitly referenced then?
>
> E.g., this one: /* will pass to dummy_numa_init */
>
> It might be me, but I find it rather confusing. After seeing that, I'd
> expect to see that, at some point, either the function returns failure
> (which of course we don't want), or a direct call dummy_numa_init().
>
> Dario
>
> --
> <<This happens because I choose it to happen!>> (Raistlin Majere)
> -----------------------------------------------------------------
> Dario Faggioli, Ph.D, http://about.me/dario.faggioli
> Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)
>



-- 
Elena
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