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

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Message-Id: <E0403A01-57FD-4232-879F-4AF14873C57E@gmail.com>
Date:	Wed, 15 Jun 2016 13:26:46 -0700
From:	Nadav Amit <nadav.amit@...il.com>
To:	Dave Hansen <dave.hansen@...ux.intel.com>
Cc:	"Anaczkowski, Lukasz" <lukasz.anaczkowski@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>,
	"kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
	"mhocko@...e.com" <mhocko@...e.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Srinivasappa, Harish" <harish.srinivasappa@...el.com>,
	"Odzioba, Lukasz" <lukasz.odzioba@...el.com>,
	"Andrejczuk, Grzegorz" <grzegorz.andrejczuk@...el.com>,
	"Daniluk, Lukasz" <lukasz.daniluk@...el.com>
Subject: Re: [PATCH v2] Linux VM workaround for Knights Landing A/D leak

Dave Hansen <dave.hansen@...ux.intel.com> wrote:

> On 06/15/2016 01:04 PM, Nadav Amit wrote:
>> Be careful here. According to the SDM when invalidating a huge-page,
>> each 4KB page needs to be invalidated separately. In practice, when
>> Linux invalidates 2MB/1GB pages it performs a full TLB flush. The
>> full flush may not be required on knights landing, and specifically
>> for the workaround, but you should check.  
> 
> Where do you get that?  The SDM says: "they (TLB invalidation operations
> invalidate all TLB entries corresponding to the translation specified by
> the paging structures.”

You are absolutely correct. Last time I write something based on my
recollection of the SDM without re-reading again. Sorry.

Nadav