From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 48F6AC0044C for ; Thu, 1 Nov 2018 08:31:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8C3592081B for ; Thu, 1 Nov 2018 08:31:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8C3592081B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728075AbeKARdY (ORCPT ); Thu, 1 Nov 2018 13:33:24 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:53030 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727753AbeKARdY (ORCPT ); Thu, 1 Nov 2018 13:33:24 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 2A0DE80D; Thu, 1 Nov 2018 01:31:24 -0700 (PDT) Received: from localhost (e113682-lin.copenhagen.arm.com [10.32.144.41]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 866623F557; Thu, 1 Nov 2018 01:31:23 -0700 (PDT) Date: Thu, 1 Nov 2018 09:31:21 +0100 From: Christoffer Dall To: Punit Agrawal Cc: kvmarm@lists.cs.columbia.edu, marc.zyngier@arm.com, will.deacon@arm.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, suzuki.poulose@arm.com, stable@vger.kernel.org Subject: Re: [PATCH v8 1/9] KVM: arm/arm64: Ensure only THP is candidate for adjustment Message-ID: <20181101083121.GG12057@e113682-lin.lund.arm.com> References: <20181001155443.23032-1-punit.agrawal@arm.com> <20181001155443.23032-2-punit.agrawal@arm.com> <20181031143646.GE12057@e113682-lin.lund.arm.com> <87h8h2rwwr.fsf@e105922-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87h8h2rwwr.fsf@e105922-lin.cambridge.arm.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 31, 2018 at 02:52:20PM +0000, Punit Agrawal wrote: > Christoffer Dall writes: > > > On Mon, Oct 01, 2018 at 04:54:35PM +0100, Punit Agrawal wrote: > >> PageTransCompoundMap() returns true for hugetlbfs and THP > >> hugepages. This behaviour incorrectly leads to stage 2 faults for > >> unsupported hugepage sizes (e.g., 64K hugepage with 4K pages) to be > >> treated as THP faults. > >> > >> Tighten the check to filter out hugetlbfs pages. This also leads to > >> consistently mapping all unsupported hugepage sizes as PTE level > >> entries at stage 2. > >> > >> Signed-off-by: Punit Agrawal > >> Reviewed-by: Suzuki Poulose > >> Cc: Christoffer Dall > >> Cc: Marc Zyngier > >> Cc: stable@vger.kernel.org # v4.13+ > > > > > > Hmm, this function is only actually called from user_mem_abort() if we > > have (!hugetlb), so I'm not sure the cc stable here was actually > > warranted, nor that this patch is strictly necessary. > > > > It doesn't hurt, and makes the code potentially more robust for the > > future though. > > > > Am I missing something? > > !hugetlb is only true for hugepage sizes supported at stage 2. The > function also got called for unsupported hugepage size at stage 2, e.g., > 64k hugepage with 4k page size, which then ended up doing the wrong > thing. > > Hope that adds some context. I should've added this to the commit log. > To be fair you did say that this was for unsupported hugepage sizes. Thanks for the explanation. Christoffer