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=-13.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 81546C28E83 for ; Fri, 4 Sep 2020 10:31:04 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 379D5206D4 for ; Fri, 4 Sep 2020 10:31:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 379D5206D4 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 A97016B0088; Fri, 4 Sep 2020 06:31:03 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9F6DE6B0089; Fri, 4 Sep 2020 06:31:03 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8750E6B008A; Fri, 4 Sep 2020 06:31:03 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0192.hostedemail.com [216.40.44.192]) by kanga.kvack.org (Postfix) with ESMTP id 639A86B0088 for ; Fri, 4 Sep 2020 06:31:03 -0400 (EDT) Received: from smtpin04.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 2A9B8824556B for ; Fri, 4 Sep 2020 10:31:03 +0000 (UTC) X-FDA: 77225011206.04.rate62_560272d270b1 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin04.hostedemail.com (Postfix) with ESMTP id E9B15800E086 for ; Fri, 4 Sep 2020 10:31:02 +0000 (UTC) X-HE-Tag: rate62_560272d270b1 X-Filterd-Recvd-Size: 4091 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf44.hostedemail.com (Postfix) with ESMTP for ; Fri, 4 Sep 2020 10:31:02 +0000 (UTC) Received: from localhost.localdomain (unknown [46.69.195.48]) (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 C4FE821582; Fri, 4 Sep 2020 10:30:59 +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 v9 12/29] arm64: mte: Tags-aware aware memcmp_pages() implementation Date: Fri, 4 Sep 2020 11:30:12 +0100 Message-Id: <20200904103029.32083-13-catalin.marinas@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200904103029.32083-1-catalin.marinas@arm.com> References: <20200904103029.32083-1-catalin.marinas@arm.com> MIME-Version: 1.0 X-Rspamd-Queue-Id: E9B15800E086 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 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: 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 @@ =20 #include #include +#include #include =20 #include @@ -23,6 +24,31 @@ void mte_sync_tags(pte_t *ptep, pte_t pte) } } =20 +int memcmp_pages(struct page *page1, struct page *page2) +{ + char *addr1, *addr2; + int ret; + + addr1 =3D page_address(page1); + addr2 =3D page_address(page2); + ret =3D 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 !=3D addr2; + + return ret; +} + void flush_mte_state(void) { if (!system_supports_mte()) diff --git a/mm/util.c b/mm/util.c index 5ef378a2a038..4e21fe7eae27 100644 --- a/mm/util.c +++ b/mm/util.c @@ -957,7 +957,7 @@ int get_cmdline(struct task_struct *task, char *buffe= r, int buflen) return res; } =20 -int memcmp_pages(struct page *page1, struct page *page2) +int __weak memcmp_pages(struct page *page1, struct page *page2) { char *addr1, *addr2; int ret;