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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id ADBDDC433EF for ; Tue, 5 Oct 2021 06:54:22 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 251D06138F for ; Tue, 5 Oct 2021 06:54:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 251D06138F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 7ABC86B006C; Tue, 5 Oct 2021 02:54:21 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 75B9B900002; Tue, 5 Oct 2021 02:54:21 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 649F56B0072; Tue, 5 Oct 2021 02:54:21 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0180.hostedemail.com [216.40.44.180]) by kanga.kvack.org (Postfix) with ESMTP id 54CC96B006C for ; Tue, 5 Oct 2021 02:54:21 -0400 (EDT) Received: from smtpin05.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 0EA55181AEF1E for ; Tue, 5 Oct 2021 06:54:21 +0000 (UTC) X-FDA: 78661469922.05.DF64E56 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf19.hostedemail.com (Postfix) with ESMTP id 6963DB000470 for ; Tue, 5 Oct 2021 06:54:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Transfer-Encoding: Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description; bh=Qr22602shIdzzG2+Obu3zaMUVwn4jZ1NQIj+6vzc1lo=; b=P4J3v3j7xLp7hyJWqzhO0yGpj8 Xjzn5UPhR+dBYwUCMfMEpEY6kBEZfZIf7h9GQU6M5KlPR4T3E9t4zWarsuxneRlYJ2WAnE9934EZa 4AME/jedTwabAuyHP8YltPfLh7l6Qjb/cLFH1TNgqIgP7p31I4jnYJVNs50AQXgRkyaasqpWcb/oq 493+ts8zxHuPj3/qjhZRsjUqrKKiupnBEv5Zw6IeKIcTNEMksRcmpYAEpuiqJw7zSueaE0dI4AGge UihAu33VdZ47vO4EhFDIY7i7rGi2o7FhFz13HZSdQ6nXlrpdS1nMWGTOFQeECFxmNE5BuxKWtBV6r i6QUTB4Q==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1mXeKW-0004jQ-1X; Tue, 05 Oct 2021 06:53:40 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id DE3739811EE; Tue, 5 Oct 2021 08:53:35 +0200 (CEST) Date: Tue, 5 Oct 2021 08:53:35 +0200 From: Peter Zijlstra To: Nadav Amit Cc: Andrew Morton , LKML , Linux-MM , Peter Xu , Andrea Arcangeli , Andrew Cooper , Andy Lutomirski , Dave Hansen , Thomas Gleixner , Will Deacon , Yu Zhao , Nick Piggin , x86@kernel.org Subject: Re: [PATCH 1/2] mm/mprotect: use mmu_gather Message-ID: <20211005065335.GG4323@worktop.programming.kicks-ass.net> References: <20210925205423.168858-1-namit@vmware.com> <20210925205423.168858-2-namit@vmware.com> <20211003121019.GF4323@worktop.programming.kicks-ass.net> <620B1A38-1457-4F77-8666-E73A318392B6@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <620B1A38-1457-4F77-8666-E73A318392B6@gmail.com> X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 6963DB000470 X-Stat-Signature: 3p6yhf8ahi7wcqi1h9edzugegra6hjdx Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=P4J3v3j7; dmarc=none; spf=none (imf19.hostedemail.com: domain of peterz@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=peterz@infradead.org X-HE-Tag: 1633416860-42298 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Oct 04, 2021 at 12:24:14PM -0700, Nadav Amit wrote: >=20 >=20 > > On Oct 3, 2021, at 5:10 AM, Peter Zijlstra wro= te: > >=20 > > On Sat, Sep 25, 2021 at 01:54:22PM -0700, Nadav Amit wrote: > >=20 > >> @@ -338,25 +344,25 @@ static unsigned long change_protection_range(s= truct vm_area_struct *vma, > >> struct mm_struct *mm =3D vma->vm_mm; > >> pgd_t *pgd; > >> unsigned long next; > >> - unsigned long start =3D addr; > >> unsigned long pages =3D 0; > >> + struct mmu_gather tlb; > >>=20 > >> BUG_ON(addr >=3D end); > >> pgd =3D pgd_offset(mm, addr); > >> flush_cache_range(vma, addr, end); > >> inc_tlb_flush_pending(mm); > >=20 > > That seems unbalanced... >=20 > Bad rebase. Thanks for catching it! >=20 > >=20 > >> + tlb_gather_mmu(&tlb, mm); > >> + tlb_start_vma(&tlb, vma); > >> do { > >> next =3D pgd_addr_end(addr, end); > >> if (pgd_none_or_clear_bad(pgd)) > >> continue; > >> - pages +=3D change_p4d_range(vma, pgd, addr, next, newprot, > >> + pages +=3D change_p4d_range(&tlb, vma, pgd, addr, next, newprot, > >> cp_flags); > >> } while (pgd++, addr =3D next, addr !=3D end); > >>=20 > >> - /* Only flush the TLB if we actually modified any entries: */ > >> - if (pages) > >> - flush_tlb_range(vma, start, end); > >> - dec_tlb_flush_pending(mm); > >=20 > > ... seeing you do remove the extra decrement. >=20 > Is it really needed? We do not put this comment elsewhere for > tlb_finish_mmu(). But no problem, I=E2=80=99ll keep it. -ENOPARSE, did you read decrement as comment? In any case, I don't particularly care about the comment, and tlb_*_mmu() imply the inc/dec thingies. All I tried to do is point out that removing the dec but leaving the inc is somewhat inconsistent :-)