From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753587AbcBJKuT (ORCPT ); Wed, 10 Feb 2016 05:50:19 -0500 Received: from mail-wm0-f54.google.com ([74.125.82.54]:38339 "EHLO mail-wm0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753030AbcBJKuQ (ORCPT ); Wed, 10 Feb 2016 05:50:16 -0500 Date: Wed, 10 Feb 2016 12:50:12 +0200 From: "Kirill A. Shutemov" To: Vineet Gupta Cc: "Kirill A. Shutemov" , "Aneesh Kumar K.V" , Andrea Arcangeli , Andrew Morton , stable@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] mm,thp: khugepaged: call pte flush at the time of collapse Message-ID: <20160210105012.GA23604@node.shutemov.name> References: <1455080175-10987-1-git-send-email-vgupta@synopsys.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1455080175-10987-1-git-send-email-vgupta@synopsys.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 10, 2016 at 10:26:15AM +0530, Vineet Gupta wrote: > This showed up on ARC when running LMBench bw_mem tests as > Overlapping TLB Machine Check Exception triggered due to STLB entry > (2M pages) overlapping some NTLB entry (regular 8K page). > > bw_mem 2m touches a large chunk of vaddr creating NTLB entries. > In the interim khugepaged kicks in, collapsing the contiguous ptes into > a single pmd. pmdp_collapse_flush()->flush_pmd_tlb_range() is called to > flush out NTLB entries for the ptes. This for ARC (by design) can only > shootdown STLB entries (for pmd). The stray NTLB entries cause the overlap > with the subsequent STLB entry for collapsed page. > So make pmdp_collapse_flush() call pte flush interface not pmd flush. > > Note that originally all thp flush call sites in generic code called > flush_tlb_range() leaving it to architecture to implement the flush for > pte and/or pmd. Commit 12ebc1581ad11454 changed this by calling a new > opt-in API flush_pmd_tlb_range() which made the semantics more explicit > but failed to distinguish the pte vs pmd flush in generic code, which is > what this patch fixes. > > Note that ARC can fixed w/o touching the generic pmdp_collapse_flush() > by defining a ARC version, but that defeats the purpose of generic > version, plus sementically this is the right thing to do. > > Fixes STAR 9000961194: LMBench on AXS103 triggering duplicate TLB > exceptions with super pages > > Cc: Kirill A. Shutemov > Cc: Aneesh Kumar K.V > Cc: Andrea Arcangeli > Cc: Andrew Morton > Cc: #4.4 > Cc: > Cc: linux-kernel@vger.kernel.org > Cc: linux-mm@kvack.org > Fixes: 12ebc1581ad11454 ("mm,thp: introduce flush_pmd_tlb_range") > Signed-off-by: Vineet Gupta Acked-by: Kirill A. Shutemov -- Kirill A. Shutemov