From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1753750AbcFOUEx (ORCPT <rfc822;w@1wt.eu>);
	Wed, 15 Jun 2016 16:04:53 -0400
Received: from mail-pf0-f194.google.com ([209.85.192.194]:33686 "EHLO
	mail-pf0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S932084AbcFOUEv convert rfc822-to-8bit (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Wed, 15 Jun 2016 16:04:51 -0400
Content-Type: text/plain; charset=us-ascii
Mime-Version: 1.0 (Mac OS X Mail 9.3 \(3124\))
Subject: Re: [PATCH v2] Linux VM workaround for Knights Landing A/D leak
From: Nadav Amit <nadav.amit@gmail.com>
In-Reply-To: <C1C2579D7BE026428F81F41198ADB17237A8670A@irsmsx110.ger.corp.intel.com>
Date: Wed, 15 Jun 2016 13:04:48 -0700
Cc: LKML <linux-kernel@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "ak@linux.intel.com" <ak@linux.intel.com>,
        "kirill.shutemov@linux.intel.com" <kirill.shutemov@linux.intel.com>,
        "mhocko@suse.com" <mhocko@suse.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        "Srinivasappa, Harish" <harish.srinivasappa@intel.com>,
        "Odzioba, Lukasz" <lukasz.odzioba@intel.com>,
        "Andrejczuk, Grzegorz" <grzegorz.andrejczuk@intel.com>,
        "Daniluk, Lukasz" <lukasz.daniluk@intel.com>
Content-Transfer-Encoding: 8BIT
Message-Id: <613007E2-2A88-4934-9364-A5A66A555305@gmail.com>
References: <7FB15233-B347-4A87-9506-A9E10D331292@gmail.com> <1465923672-14232-1-git-send-email-lukasz.anaczkowski@intel.com> <76F6D5F2-6723-441B-BD63-52628731F1FF@gmail.com> <C1C2579D7BE026428F81F41198ADB17237A8670A@irsmsx110.ger.corp.intel.com>
To: "Anaczkowski, Lukasz" <lukasz.anaczkowski@intel.com>
X-Mailer: Apple Mail (2.3124)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Lukasz <lukasz.anaczkowski@intel.com> wrote:

> From: Nadav Amit [mailto:nadav.amit@gmail.com] 
> Sent: Tuesday, June 14, 2016 8:38 PM
> 
>>> +	pte_t pte = ptep_get_and_clear(mm, addr, ptep);
>>> +
>>> +	if (boot_cpu_has_bug(X86_BUG_PTE_LEAK))
>>> +		fix_pte_leak(mm, addr, ptep);
>>> +	return pte;
>>> }
>> 
>> I missed it on the previous iteration: ptep_get_and_clear already calls 
>> fix_pte_leak when needed. So do you need to call it again here?
> 
> You're right, Nadav. Not needing this. Will be removed in next version of the patch.

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.  

Regards,
Nadav