From patchwork Wed Jun 24 17:52:29 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Catalin Marinas X-Patchwork-Id: 11624005 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 9BF5B14F6 for ; Wed, 24 Jun 2020 17:59:05 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 66847207DD for ; Wed, 24 Jun 2020 17:59:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="vwX/TDUb" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 66847207DD 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-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To:Message-Id:Date: Subject:To:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=9XhQ60LBqJILIn5Ic01HTRsNDnkvyn7XKXlHQIVZk5o=; b=vwX/TDUb+ej3NmJcnDeds56bX pCKEWu7OaE1//JBvlh/flLGMRTfrupOrG2OOesDk3ThRLaW3YqttTeA5RIjg7PRdxla4h6gbvHeVa 1XsLjLnRE2s6Gs8DpCgNNacQubLNFy8Mmw/RSD71NlRPlrm/1ZylKKetfgQZ16VytyzKSi3e7Yf6q BD1P53enbAe4Yp+7qvjQFqFAw84KlBx5fEXXkzXOMfxORuvyyrBrZ5HEqFzgM3IW6xcEt8owswjTw /NTuhVji4Ds6yDOs8yToJvzeDBmuZ+crZzn9vi62G8HKPxWH4X70ugdHPyjOvL7INrWzM/CfysDPn xjZlTfm4Q==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jo9dK-0005ry-8D; Wed, 24 Jun 2020 17:56:26 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jo9aC-0004BO-Pc for linux-arm-kernel@lists.infradead.org; Wed, 24 Jun 2020 17:53:15 +0000 Received: from localhost.localdomain (unknown [2.26.170.173]) (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 891F42077D; Wed, 24 Jun 2020 17:53:09 +0000 (UTC) From: Catalin Marinas To: linux-arm-kernel@lists.infradead.org Subject: [PATCH v5 10/25] arm64: mte: Tags-aware aware memcmp_pages() implementation Date: Wed, 24 Jun 2020 18:52:29 +0100 Message-Id: <20200624175244.25837-11-catalin.marinas@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200624175244.25837-1-catalin.marinas@arm.com> References: <20200624175244.25837-1-catalin.marinas@arm.com> MIME-Version: 1.0 X-Spam-Note: CRM114 invocation failed X-Spam-Score: -5.0 (-----) X-Spam-Report: SpamAssassin version 3.4.4 on merlin.infradead.org summary: Content analysis details: (-5.0 points) pts rule name description ---- ---------------------- -------------------------------------------------- -5.0 RCVD_IN_DNSWL_HI RBL: Sender listed at https://www.dnswl.org/, high trust [198.145.29.99 listed in list.dnswl.org] 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.0 SPF_PASS SPF: sender matches SPF record 0.0 HEADER_FROM_DIFFERENT_DOMAINS From and EnvelopeFrom 2nd level mail domains are different X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, Szabolcs Nagy , Andrey Konovalov , Kevin Brodsky , Peter Collingbourne , linux-mm@kvack.org, Andrew Morton , Vincenzo Frascino , Will Deacon , Dave P Martin Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org 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;