From patchwork Fri Jul 3 15:37:03 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Catalin Marinas X-Patchwork-Id: 11642063 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 4118792A for ; Fri, 3 Jul 2020 15:37:54 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 0B39621927 for ; Fri, 3 Jul 2020 15:37:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0B39621927 Authentication-Results: mail.kernel.org; dmarc=none (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 F0C668D0079; Fri, 3 Jul 2020 11:37:50 -0400 (EDT) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id E1D618D0074; Fri, 3 Jul 2020 11:37:50 -0400 (EDT) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CBEB48D0079; Fri, 3 Jul 2020 11:37:50 -0400 (EDT) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0043.hostedemail.com [216.40.44.43]) by kanga.kvack.org (Postfix) with ESMTP id A85708D0074 for ; Fri, 3 Jul 2020 11:37:50 -0400 (EDT) Received: from smtpin26.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 5D821824556B for ; Fri, 3 Jul 2020 15:37:50 +0000 (UTC) X-FDA: 76997169900.26.fog84_37113cc26e93 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin26.hostedemail.com (Postfix) with ESMTP id 3D4AF1804A300 for ; Fri, 3 Jul 2020 15:37:50 +0000 (UTC) X-Spam-Summary: 1,0,0,df121fe6058133b3,d41d8cd98f00b204,srs0=nzee=ao=arm.com=catalin.marinas@kernel.org,,RULES_HIT:41:355:379:541:800:960:968:973:988:989:1260:1311:1314:1345:1359:1431:1437:1515:1534:1542:1711:1730:1747:1777:1792:1981:2194:2199:2393:2553:2559:2562:2693:3138:3139:3140:3141:3142:3354:3865:3866:3867:3868:3870:3871:3872:4250:4321:4605:5007:6119:6261:7875:10004:11026:11232:11658:11914:12291:12296:12297:12517:12519:12555:12986:13180:13229:13894:14040:14096:14181:14394:14721:21063:21080:21230:21451:21627:21990:30054:30055:30070:30090,0,RBL:198.145.29.99:@kernel.org:.lbl8.mailshell.net-64.100.201.201 62.2.0.100;04yrfue4ftj8kfk77pyudduqybc4mypkwgpt3neimt9zo5qiictka9sx6q373mq.8kpk9i4yr169rws6hqs9x7wrsqt8dr585jufjtritonuy56qzdfomps7fp4b4tn.q-lbl8.mailshell.net-223.238.255.100,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fp,MSBL:0,DNSBL:neutral,Custom_rules:0:0:0,LFtime:24,LUA_SUMMARY:none X-HE-Tag: fog84_37113cc26e93 X-Filterd-Recvd-Size: 4093 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf38.hostedemail.com (Postfix) with ESMTP for ; Fri, 3 Jul 2020 15:37:49 +0000 (UTC) Received: from localhost.localdomain (unknown [95.146.230.158]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 46503215A4; Fri, 3 Jul 2020 15:37:47 +0000 (UTC) From: Catalin Marinas To: linux-arm-kernel@lists.infradead.org Cc: linux-mm@kvack.org, linux-arch@vger.kernel.org, Will Deacon , Dave P Martin , Vincenzo Frascino , Szabolcs Nagy , Kevin Brodsky , Andrey Konovalov , Peter Collingbourne , Andrew Morton Subject: [PATCH v6 11/26] arm64: mte: Tags-aware aware memcmp_pages() implementation Date: Fri, 3 Jul 2020 16:37:03 +0100 Message-Id: <20200703153718.16973-12-catalin.marinas@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200703153718.16973-1-catalin.marinas@arm.com> References: <20200703153718.16973-1-catalin.marinas@arm.com> MIME-Version: 1.0 X-Rspamd-Queue-Id: 3D4AF1804A300 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 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: When the Memory Tagging Extension is enabled, two pages are identical only if both their data and tags are identical. Make the generic memcmp_pages() a __weak function and add an arm64-specific implementation which returns non-zero if any of the two pages contain valid MTE tags (PG_mte_tagged set). There isn't much benefit in comparing the tags of two pages since these are normally used for heap allocations and likely to differ anyway. Co-developed-by: Vincenzo Frascino Signed-off-by: Vincenzo Frascino Signed-off-by: Catalin Marinas Cc: Will Deacon --- Notes: v4: - Remove page tag comparison. This is not very useful to detect identical pages as long as set_pte_at() can zero the tags on a page without copy-on-write if mapped with PROT_MTE. This can be improved if a real case appears but it's unlikely for heap pages to be identical across multiple processes. - Move the memcmp_pages() function to mte.c. arch/arm64/kernel/mte.c | 26 ++++++++++++++++++++++++++ mm/util.c | 2 +- 2 files changed, 27 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c index 5bf9bbed5a25..5f54fd140610 100644 --- a/arch/arm64/kernel/mte.c +++ b/arch/arm64/kernel/mte.c @@ -5,6 +5,7 @@ #include #include +#include #include #include @@ -23,6 +24,31 @@ void mte_sync_tags(pte_t *ptep, pte_t pte) } } +int memcmp_pages(struct page *page1, struct page *page2) +{ + char *addr1, *addr2; + int ret; + + addr1 = page_address(page1); + addr2 = page_address(page2); + ret = memcmp(addr1, addr2, PAGE_SIZE); + + if (!system_supports_mte() || ret) + return ret; + + /* + * If the page content is identical but at least one of the pages is + * tagged, return non-zero to avoid KSM merging. If only one of the + * pages is tagged, set_pte_at() may zero or change the tags of the + * other page via mte_sync_tags(). + */ + if (test_bit(PG_mte_tagged, &page1->flags) || + test_bit(PG_mte_tagged, &page2->flags)) + return addr1 != addr2; + + return ret; +} + void flush_mte_state(void) { if (!system_supports_mte()) diff --git a/mm/util.c b/mm/util.c index c63c8e47be57..c856f5fec69d 100644 --- a/mm/util.c +++ b/mm/util.c @@ -911,7 +911,7 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen) return res; } -int memcmp_pages(struct page *page1, struct page *page2) +int __weak memcmp_pages(struct page *page1, struct page *page2) { char *addr1, *addr2; int ret;