linux-kernel - Re: [PATCH v3] x86: move cacheinfo sysfs to generic cacheinfo infrastructure

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Date:	Tue, 10 Mar 2015 14:35:12 +0000
From:	Sudeep Holla <sudeep.holla@....com>
To:	Borislav Petkov <bp@...e.de>
CC:	Sudeep Holla <sudeep.holla@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andre Przywara <Andre.Przywara@....com>,
	"x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH v3] x86: move cacheinfo sysfs to generic cacheinfo infrastructure



On 10/03/15 14:26, Borislav Petkov wrote:
> On Tue, Mar 10, 2015 at 02:22:22PM +0000, Sudeep Holla wrote:
>> I was able to reproduce this and now I realise I had CONFIG_AMD_NB
>> disabled in my config earlier which hid this issue previously, sorry
>> for that.
>>
>> The below patch fixed the issue on my Intel i7 box. I can post this
>> separately if required.
>>
>> Regards,
>> Sudeep
>>
>>  From b081cbf26071f4c8ce51f270931387415ab1a06c Mon Sep 17 00:00:00 2001
>> From: Sudeep Holla <sudeep.holla@....com>
>> Date: Tue, 10 Mar 2015 13:49:58 +0000
>> Subject: [PATCH] x86: cacheinfo: fix cache_get_priv_group for Intel
>> processors
>>
>> The private pointer provided by the cacheinfo is used to implement
>> the AMD L3 cache specific attributes using the northbridge pointer
>> obtained through cpuid4 registers. However, it's populated even on
>> Intel processors for Level 3 cache. This results in failure of
>
> Do we need it populated on Intel?
>
> Because if not, we can leave it NULL there and do only
>
> 	if (this_leaf->level < 3 || !nb)
> 		return NULL;
>

Yes we can do that. I leave that too you guys. I don't know the exact
reason why cpuid4_cache_lookup_regs is populating
	struct amd_northbridge *nb in struct _cpuid4_info_reg

My initial assumption was that it will be NULL for Intel processors and
hence I assigned cacheinfo->priv to nb pointer unconditionally.
So I don't have any strong opinion here.

Regards,
Sudeep

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