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=-5.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 6328BC433FF for ; Mon, 5 Aug 2019 17:06:52 +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 30C81216B7 for ; Mon, 5 Aug 2019 17:06:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="LWk3qYAn" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 30C81216B7 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:References: Message-ID:Subject: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=Xu3/BIaop1OsTRrCTo0Yxgca51oF8d8gJhnwCdTkn4k=; b=LWk3qYAnqYKrwJ cxtYBYm8Jt4eHhWS1y+UPXGuwFFyEk5Lggs6pxLJd9tX9QjYm+NtBtEeBulsnpy7+d0l/aGBF//kQ KF5gibcqEI2GPFKL+Cg46s02QbFPhd0oUoqwSlokYI/ToZxrzviPdpjVIwzoy2Z90smsJDhVJWFvG UyRPeDEtjZidb9EUPBBdbEzvfQEgSBChImLkJpoHPm+9wmaMeC9D5i9m783KVSU8SMmQXvW27wyXX BbywcjHkLnxJD1BHfgdY43GpsvSOe5QtTpG1kuuILD05BoY16esSK7RzjDeE8X7aOdneIqyKDj8xk Ttx0XM3TEucXYRzacJnw==; 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 1hugRZ-0000xD-Ob; Mon, 05 Aug 2019 17:06:45 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hugRW-0000wt-Rk for linux-arm-kernel@lists.infradead.org; Mon, 05 Aug 2019 17:06:44 +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 48218344; Mon, 5 Aug 2019 10:06:41 -0700 (PDT) Received: from arrakis.emea.arm.com (arrakis.cambridge.arm.com [10.1.196.78]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 44CBE3F694; Mon, 5 Aug 2019 10:06:40 -0700 (PDT) Date: Mon, 5 Aug 2019 18:06:38 +0100 From: Catalin Marinas To: Steve Capper Subject: Re: [PATCH V4 07/11] arm64: mm: Logic to make offset_ttbr1 conditional Message-ID: <20190805170637.GH4175@arrakis.emea.arm.com> References: <20190729162117.832-1-steve.capper@arm.com> <20190729162117.832-8-steve.capper@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190729162117.832-8-steve.capper@arm.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-20190805_100642_940563_9F2C0E3E X-CRM114-Status: GOOD ( 13.91 ) 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: crecklin@redhat.com, ard.biesheuvel@linaro.org, maz@kernel.org, bhsharma@redhat.com, will@kernel.org, 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 On Mon, Jul 29, 2019 at 05:21:13PM +0100, Steve Capper wrote: > When running with a 52-bit userspace VA and a 48-bit kernel VA we offset > ttbr1_el1 to allow the kernel pagetables with a 52-bit PTRS_PER_PGD to > be used for both userspace and kernel. > > Moving on to a 52-bit kernel VA we no longer require this offset to > ttbr1_el1 should we be running on a system with HW support for 52-bit > VAs. > > This patch introduces conditional logic to offset_ttbr1 to query > SYS_ID_AA64MMFR2_EL1 whenever 52-bit VAs are selected. If there is HW > support for 52-bit VAs then the ttbr1 offset is skipped. > > We choose to read a system register rather than vabits_actual because > offset_ttbr1 can be called in places where the kernel data is not > actually mapped. > > Calls to offset_ttbr1 appear to be made from rarely called code paths so > this extra logic is not expected to adversely affect performance. > > Signed-off-by: Steve Capper Reviewed-by: Catalin Marinas _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel