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Subject: Re: [PATCH v2] Linux VM workaround for Knights Landing A/D leak
From: Nadav Amit <nadav.amit@gmail.com>
In-Reply-To: <5761B630.7020502@linux.intel.com>
Date: Wed, 15 Jun 2016 13:26:46 -0700
Cc: "Anaczkowski, Lukasz" <lukasz.anaczkowski@intel.com>,
        LKML <linux-kernel@vger.kernel.org>,
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        "Odzioba, Lukasz" <lukasz.odzioba@intel.com>,
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To: Dave Hansen <dave.hansen@linux.intel.com>
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Dave Hansen <dave.hansen@linux.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