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=-4.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 59554C433EF for ; Mon, 6 Sep 2021 18:00:33 +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 20B186101C for ; Mon, 6 Sep 2021 18:00:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 20B186101C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=Z1HDf56FpCdroiAN4UO0enXcuRNSmIRosHzrby84dwM=; b=yi9YUCf/ATySOQ L5Vf4Ap7EsBmqUnT2ApanlAAWnnG9vR6OxX7xAt6DpZnLB5QRN+f37RJpmN6QlqtXbUB7w2Ss8j4x dUE28iK71lL+jFPxQdqjNnSFhckk6EJG0jfEwVjKf1fFuidHiDydvGwGwnNWBkuwl7uLGBFnZM7xw JhqaSFWLD3gUIXqRO9/ChkAr9jDQ08+L9pId9Jlt/6aZYMZtnha0u6vXE2DUgF6vvLNQx3XKS2aCm 6shcs0KcbJJWglbZuMKWQ70FpwsjyWJbeKvIasQJ8jXwmmbLPnHIZABTRgXtesL5bQXITW53/KlUG xV9546VlnzYB45fZfxzA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mNIt8-001UCI-RZ; Mon, 06 Sep 2021 17:58:34 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mNIt5-001UBm-PK for linux-arm-kernel@lists.infradead.org; Mon, 06 Sep 2021 17:58:33 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id AAC3360F92; Mon, 6 Sep 2021 17:58:29 +0000 (UTC) Date: Mon, 6 Sep 2021 18:58:26 +0100 From: Catalin Marinas To: Peter Collingbourne Cc: Vincenzo Frascino , Will Deacon , Andrey Konovalov , Evgenii Stepanov , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] arm64: kasan: mte: move GCR_EL1 switch to task switch when KASAN disabled Message-ID: References: <20210827030748.587710-1-pcc@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210827030748.587710-1-pcc@google.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210906_105831_884327_13BD53DA X-CRM114-Status: GOOD ( 12.57 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Aug 26, 2021 at 08:07:48PM -0700, Peter Collingbourne wrote: > It is not necessary to write to GCR_EL1 on every kernel entry and > exit when HW tag-based KASAN is disabled because the kernel will not > execute any IRG instructions in that mode. Since accessing GCR_EL1 > can be expensive on some microarchitectures, avoid doing so by moving > the access to task switch when HW tag-based KASAN is disabled. I haven't got a chance to look at this patch yet as it was posted pretty close to the merging window, so it wasn't on my urgent list (not a fix). What's the use-case exactly? Do you expect production kernels to have KASAN_HW built in but disabled on the command line? I thought there's an overhead already from kasan even without MTE. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel