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=-9.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 5E23DC282CD for ; Mon, 28 Jan 2019 17:32:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2AB522147A for ; Mon, 28 Jan 2019 17:32:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548696762; bh=smksVjHmBgGlBWiX3aftH5cmLjUKG7JYTo/oSFQbUcM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=qJ428ieD/PpLaWZkinDQB6Ijx25m1vVrghAMNvI51vxCdK1+AlpP9TYmyFpr0NxYA oE0Ji/+iPz1fqVQALmL3nbhfQUOjcFf6qnrbLjjBRl+O0yo7+Vk+BRj2oKtrRG4S/i F2RtzrgtlvU3B4em5XOoQepo0QlvEJYQzdAXdyFQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730643AbfA1Rck (ORCPT ); Mon, 28 Jan 2019 12:32:40 -0500 Received: from mail.kernel.org ([198.145.29.99]:42868 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730209AbfA1P5V (ORCPT ); Mon, 28 Jan 2019 10:57:21 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (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 E6ABC20881; Mon, 28 Jan 2019 15:57:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548691041; bh=smksVjHmBgGlBWiX3aftH5cmLjUKG7JYTo/oSFQbUcM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Zls735vXYgZFuxsfS0UxjwvI18IhPGeVdWWvyW0RpLD32Udh5dygo667JcGeZesE0 tLzJV7FXw18bFKPi9crn6574F0zFDWe8VrgJmV1bHPaZOjpbfoU52ulQQgS3j81Qxg 7GR72EYwi3cPCIpNHJOyURTJcvch2ztPISATJmic= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Anton Ivanov , Richard Weinberger , Sasha Levin , linux-um@lists.infradead.org Subject: [PATCH AUTOSEL 4.20 271/304] um: Avoid marking pages with "changed protection" Date: Mon, 28 Jan 2019 10:43:08 -0500 Message-Id: <20190128154341.47195-271-sashal@kernel.org> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20190128154341.47195-1-sashal@kernel.org> References: <20190128154341.47195-1-sashal@kernel.org> MIME-Version: 1.0 X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Anton Ivanov [ Upstream commit 8892d8545f2d0342b9c550defbfb165db237044b ] Changing protection is a very high cost operation in UML because in addition to an extra syscall it also interrupts mmap merge sequences generated by the tlb. While the condition is not particularly common it is worth avoiding. Signed-off-by: Anton Ivanov Signed-off-by: Richard Weinberger Signed-off-by: Sasha Levin --- arch/um/include/asm/pgtable.h | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/arch/um/include/asm/pgtable.h b/arch/um/include/asm/pgtable.h index 7485398d0737..9c04562310b3 100644 --- a/arch/um/include/asm/pgtable.h +++ b/arch/um/include/asm/pgtable.h @@ -197,12 +197,17 @@ static inline pte_t pte_mkold(pte_t pte) static inline pte_t pte_wrprotect(pte_t pte) { - pte_clear_bits(pte, _PAGE_RW); + if (likely(pte_get_bits(pte, _PAGE_RW))) + pte_clear_bits(pte, _PAGE_RW); + else + return pte; return(pte_mknewprot(pte)); } static inline pte_t pte_mkread(pte_t pte) { + if (unlikely(pte_get_bits(pte, _PAGE_USER))) + return pte; pte_set_bits(pte, _PAGE_USER); return(pte_mknewprot(pte)); } @@ -221,6 +226,8 @@ static inline pte_t pte_mkyoung(pte_t pte) static inline pte_t pte_mkwrite(pte_t pte) { + if (unlikely(pte_get_bits(pte, _PAGE_RW))) + return pte; pte_set_bits(pte, _PAGE_RW); return(pte_mknewprot(pte)); } -- 2.19.1