linux-kernel - Re: [PATCH v2] Linux VM workaround for Knights Landing A/D leak

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Message-ID: <576052E0.3050408@linux.intel.com>
Date:	Tue, 14 Jun 2016 11:54:24 -0700
From:	Dave Hansen <dave.hansen@...ux.intel.com>
To:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
Cc:	Lukasz Anaczkowski <lukasz.anaczkowski@...el.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	tglx@...utronix.de, mingo@...hat.com, ak@...ux.intel.com,
	kirill.shutemov@...ux.intel.com, mhocko@...e.com,
	akpm@...ux-foundation.org, hpa@...or.com,
	harish.srinivasappa@...el.com, lukasz.odzioba@...el.com,
	grzegorz.andrejczuk@...el.com, lukasz.daniluk@...el.com,
	Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH v2] Linux VM workaround for Knights Landing A/D leak

On 06/14/2016 11:34 AM, One Thousand Gnomes wrote:
> On Tue, 14 Jun 2016 10:24:16 -0700
> Dave Hansen <dave.hansen@...ux.intel.com> wrote:
> 
>> On 06/14/2016 10:01 AM, Lukasz Anaczkowski wrote:
>>> v2 (Lukasz Anaczkowski):
>>>     () fixed compilation breakage  
>> ...
>>
>> By unconditionally defining the workaround code, even on kernels where
>> there is no chance of ever hitting this bug.  I think that's a pretty
>> poor way to do it.
>>
>> Can we please stick this in one of the intel.c files, so it's only
>> present on CPU_SUP_INTEL builds?
> 
> Can we please make it use alternatives or somesuch so that it just goes
> away at boot if its not a Knights Landing box ?

Lukasz, Borislav suggested using static_cpu_has_bug(), which will do the
alternatives patching.  It's definitely the right thing to use here.