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=-5.6 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,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 C0BE4C11F68 for ; Fri, 2 Jul 2021 17:46:32 +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 84C4E6140E for ; Fri, 2 Jul 2021 17:46:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 84C4E6140E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+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.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=6QdKYNzCPGOiym26f6U4Zq/nmW+1OFbHnPhO8jPOys8=; b=4u+O4/iVXZ+LIX yf1o9Murb6bbx/sLmJCzJ4hhRAjkE83z4GiUEwNSMnnw8Avuf5EptOP/Ngl2+9yndT3aZAOwuyskv 0DFMfF7FU5xU80gLNPwY+u6uh04BRwBOHKbCl9uQeVre3PwVh1N5aX8V4oQyx8gsdEEguyW3GrRdX Ze/fXhYo+IUpwS58QuP8VdwrWcD+RuyFwUiWXT5RAb/KplLlhmzsvc86SvR26z32qYot3t9ltl5JW 6JB16T69j4mcEr3A/1Cis5PHlpqbLIzn+bHd8sZA5x0x4I74Le9n7cl7Al5DaLaKVeSteQ46Q9R/t px3OuvdurD6V/4Npc1Jg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1lzNDv-003f9y-Nu; Fri, 02 Jul 2021 17:45:07 +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 1lzNDj-003f05-98 for linux-arm-kernel@lists.infradead.org; Fri, 02 Jul 2021 17:44:56 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id 2465661353; Fri, 2 Jul 2021 17:44:53 +0000 (UTC) Date: Fri, 2 Jul 2021 18:44:50 +0100 From: Catalin Marinas To: Peter Collingbourne Cc: Vincenzo Frascino , Will Deacon , Andrey Konovalov , Evgenii Stepanov , Szabolcs Nagy , Tejas Belagod , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] arm64: mte: switch GCR_EL1 on task switch rather than entry/exit Message-ID: <20210702174450.GC685@arm.com> References: <20210702031922.1291398-1-pcc@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210702031922.1291398-1-pcc@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210702_104455_549025_9D1C65F7 X-CRM114-Status: GOOD ( 10.18 ) 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, Jul 01, 2021 at 08:19:22PM -0700, Peter Collingbourne wrote: > Accessing GCR_EL1 and issuing an ISB can be expensive on some > microarchitectures. To avoid taking this performance hit on every > kernel entry/exit, switch GCR_EL1 on task switch rather than > entry/exit. Is it the ISB that's causing issues or the MRS/MSR as well? I think we can avoid the ISB when PtrAuth is enabled by shuffling the entry code a bit. We can also simplify the mte_set_gcr macro to avoid an MRS. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel