linux-kernel - Re: [patch 3/3] x86: cache_info: Kill the atomic allocation in amd_init_l3

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Date:	Sun, 24 Jul 2011 18:13:38 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Borislav Petkov <bp@...en8.de>
cc:	LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
	Hans Rosenfeld <hans.rosenfeld@....com>,
	Borislav Petkov <borislav.petkov@....com>,
	Andreas Herrmann <andreas.herrmann3@....com>,
	Mike Travis <travis@....com>
Subject: Re: [patch 3/3] x86: cache_info: Kill the atomic allocation in
 amd_init_l3_cache()

On Sun, 24 Jul 2011, Borislav Petkov wrote:
> On Sun, Jul 24, 2011 at 09:46:09AM -0000, Thomas Gleixner wrote:
> >  
> >  	/* only for L3, and not in virtualized environments */
> > -	if (index < 3 || amd_nb_num() == 0)
> > +	if (index < 3)
> >  		return;
> 
> AFAICT, we still need the "amd_nb_num() == 0" check for xen because it
> doesn't export NB PCI devices to the guest, see f2b20e41...
> 
> >  
> > -	/*
> > -	 * Strictly speaking, the amount in @size below is leaked since it is
> > -	 * never freed but this is done only on shutdown so it doesn't matter.
> > -	 */
> > -	if (!l3_caches) {
> > -		int size = amd_nb_num() * sizeof(struct amd_l3_cache);
> > -
> > -		l3_caches = kzalloc(size, GFP_ATOMIC);
> > -		if (!l3_caches)
> > -			return;
> > -	}
> > -
> >  	node = amd_get_nb_id(smp_processor_id());
> > -
> > -	if (!l3_caches[node].nb) {
> > -		l3_caches[node].nb = node_to_amd_nb(node);
> > -		amd_calc_l3_indices(&l3_caches[node]);
> > -	}
> > -
> > -	this_leaf->l3 = &l3_caches[node];
> > +	this_leaf->nb = node_to_amd_nb(node);
> 
> although, on a second thought, node_to_amd_nb(node) should return NULL
> since the AMD NB caching code shouldnt've enumerated any NB devices and
> 
> > +	if (this_leaf->nb && !this_leaf->nb->l3_cache.indices)
> > +		amd_calc_l3_indices(this_leaf->nb);
> 
> this check should fail. Hm.

Right, that was my thought.
 
> Let me test the patchset on Monday to verify there are no other subtle
> interactions I haven't thought of right now.

Thanks,

	tglx
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