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=-10.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 36F09C433B4 for ; Wed, 12 May 2021 12:12:53 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A13D661285 for ; Wed, 12 May 2021 12:12:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A13D661285 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 154D56B0036; Wed, 12 May 2021 08:12:52 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 12D3B6B006E; Wed, 12 May 2021 08:12:52 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 042A66B0070; Wed, 12 May 2021 08:12:51 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0044.hostedemail.com [216.40.44.44]) by kanga.kvack.org (Postfix) with ESMTP id DC9B76B0036 for ; Wed, 12 May 2021 08:12:51 -0400 (EDT) Received: from smtpin17.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 93A6240EE for ; Wed, 12 May 2021 12:12:51 +0000 (UTC) X-FDA: 78132467742.17.34C18B0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf07.hostedemail.com (Postfix) with ESMTP id CE8CEA001AB0 for ; Wed, 12 May 2021 12:12:47 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 9D4636109E; Wed, 12 May 2021 12:12:48 +0000 (UTC) Date: Wed, 12 May 2021 13:12:46 +0100 From: Catalin Marinas To: Peter Collingbourne Cc: Andrey Konovalov , Alexander Potapenko , Vincenzo Frascino , Andrew Morton , Evgenii Stepanov , linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2 2/3] arm64: mte: handle tags zeroing at page allocation time Message-ID: <20210512121245.GE14638@arm.com> References: <69431af7c7d5a0688ef2aacc9e51949415df8325.1620777151.git.pcc@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <69431af7c7d5a0688ef2aacc9e51949415df8325.1620777151.git.pcc@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Rspamd-Queue-Id: CE8CEA001AB0 Authentication-Results: imf07.hostedemail.com; dkim=none; spf=pass (imf07.hostedemail.com: domain of cmarinas@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=cmarinas@kernel.org; dmarc=fail reason="SPF not aligned (relaxed), No valid DKIM" header.from=arm.com (policy=none) X-Rspamd-Server: rspam03 X-Stat-Signature: rqtb33484np6kgcxo1yrnkiii9oonza6 Received-SPF: none (kernel.org>: No applicable sender policy available) receiver=imf07; identity=mailfrom; envelope-from=""; helo=mail.kernel.org; client-ip=198.145.29.99 X-HE-DKIM-Result: none/none X-HE-Tag: 1620821567-463825 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 Tue, May 11, 2021 at 04:54:25PM -0700, Peter Collingbourne wrote: > Currently, on an anonymous page fault, the kernel allocates a zeroed > page and maps it in user space. If the mapping is tagged (PROT_MTE), > set_pte_at() additionally clears the tags. It is, however, more > efficient to clear the tags at the same time as zeroing the data on > allocation. To avoid clearing the tags on any page (which may not be > mapped as tagged), only do this if the vma flags contain VM_MTE. This > requires introducing a new GFP flag that is used to determine whether > to clear the tags. > > The DC GZVA instruction with a 0 top byte (and 0 tag) requires > top-byte-ignore. Set the TCR_EL1.{TBI1,TBID1} bits irrespective of > whether KASAN_HW is enabled. > > Signed-off-by: Peter Collingbourne > Co-developed-by: Catalin Marinas > Signed-off-by: Catalin Marinas > Link: https://linux-review.googlesource.com/id/Id46dc94e30fe11474f7e54f5d65e7658dbdddb26 Reviewed-by: Catalin Marinas