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=-2.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 0C063C3A5A1 for ; Wed, 28 Aug 2019 11:13:06 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 CFC362189D for ; Wed, 28 Aug 2019 11:13:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="ctUvXolL" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CFC362189D 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+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date: Message-ID:From:References:To:Subject:Reply-To:Content-ID:Content-Description :Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=bJxDFOHfqd2kXQgwHGmx+CO7LurCr+ti3wu5qNUEuNE=; b=ctUvXolLSh/KYn 53YKpQGpsMVWbfR/8X6yI5UkMX2Y14EtkTZecJJT/Xuf4EDksUBFbQEFfUnK9TJMridZ7TR3fC/5q WxEq1dI5ifsnxsL1szoxp8lcC7BqjKVcFnpLqjLL7YG8rgFF8rvwH5Rx2jqGEjcJNZJTeRwZTF6Mo QyAB3kRAsgmo92wzZ6JHt0pW3XkxchIlWyHMqsVi2/jxO65phDSfKuU9dgvSr+kF1EfMjdtleqtnz ov4luZ3azx4mG5iDb9tbm524vUmu4gpRMJwmrVwEfHU4JUznY7sauzGWSXHmGxirN8VX6S19aYlEN XIScnr6wMb6Cmnz0lIEA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1i2vsm-0005En-OZ; Wed, 28 Aug 2019 11:12:56 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1i2vsA-0004kf-DC for linux-arm-kernel@lists.infradead.org; Wed, 28 Aug 2019 11:12:21 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 3B932337; Wed, 28 Aug 2019 04:12:17 -0700 (PDT) Received: from [10.1.196.105] (eglon.cambridge.arm.com [10.1.196.105]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8DE4E3F246; Wed, 28 Aug 2019 04:12:16 -0700 (PDT) Subject: Re: [PATCH] arm64: kpti: ensure patched kernel text is fetched from PoU To: Mark Rutland References: <20190827171257.36023-1-mark.rutland@arm.com> From: James Morse Message-ID: <86e5726b-70ed-e930-9b62-ac74b083af6b@arm.com> Date: Wed, 28 Aug 2019 12:12:14 +0100 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20190827171257.36023-1-mark.rutland@arm.com> Content-Language: en-GB X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190828_041218_534193_7432CBF9 X-CRM114-Status: GOOD ( 12.94 ) 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: Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Mark, On 27/08/2019 18:12, Mark Rutland wrote: > While the MMUs is disabled, I-cache speculation can result in (Nit: MMU) > instructions being fetched from the PoC. During boot we may patch > instructions (e.g. for alternatives and jump labels), and these may be > dirty at the PoU (and stale at the PoC). > > Thus, while the MMU is disabled in the KPTI pagetable fixup code we may > load stale instructions into the I-cache, potentially leading to > subsequent crashes when executing regions of code which have been > modified at runtime. > > Similarly to commit: > > 8ec41987436d566f ("arm64: mm: ensure patched kernel text is fetched from PoU") > > ... we can invalidate the I-cache after enabling the MMU to prevent such > issues. > The KPTI pagetable fixup code itself should be clean to the PoC per the > boot protocol, so no maintenance is required for this code. Reviewed-by: James Morse Thanks, James _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel