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=-6.5 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 BDA3EC4363D for ; Thu, 24 Sep 2020 10:12:21 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (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 6CCD321D24 for ; Thu, 24 Sep 2020 10:12:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="n9gHtLS3" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6CCD321D24 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux.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=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:References:Message-ID:In-Reply-To: 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=tePgbbkpxcMvUIkACyFix2tyh265NhkoJpcQoBTIBT0=; b=n9gHtLS3S+3OWcEhiLwGYvZgT cTgRggPRm1LQiFgXPSYs8UFXpgnBUx06rsnD5ecEO9HQYclHJYjrzNUMYxScfYH1/ZiDBaixV/p7b Buadb3hlsGeRov22zJS7Y9FN/ZMM7KNB951EQQl+f5L6BzG/alla+Xxg6wjVNbSQDb7f66vfkAT8T f2TOeCnVSbvHO6K6wXHDpgpgdpeXeWQPRhoDmRGdpJmKcuC0vC9QIMyiI9+qzdarWBYX+Elr7au76 vx/0zlGJ8lIH79QzmH3GC92dEfvMDjNAYGzOcr5xT79KsjIloxuCDonybxwZj0SpuMNDZEwlN2ZJ3 6vu0aR/cw==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kLODL-0002t1-Lv; Thu, 24 Sep 2020 10:10:59 +0000 Received: from gentwo.org ([3.19.106.255]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kLODI-0002rz-Aj for linux-arm-kernel@lists.infradead.org; Thu, 24 Sep 2020 10:10:57 +0000 Received: by gentwo.org (Postfix, from userid 1002) id D7A6C3F1AE; Thu, 24 Sep 2020 10:10:52 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by gentwo.org (Postfix) with ESMTP id D4FD23F1AA; Thu, 24 Sep 2020 10:10:52 +0000 (UTC) Date: Thu, 24 Sep 2020 10:10:52 +0000 (UTC) From: Christopher Lameter X-X-Sender: cl@www.lameter.com To: David Brazdil Subject: Re: [PATCH v4 00/10] Independent per-CPU data section for nVHE In-Reply-To: <20200922204910.7265-1-dbrazdil@google.com> Message-ID: References: <20200922204910.7265-1-dbrazdil@google.com> User-Agent: Alpine 2.22 (DEB 394 2020-01-19) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200924_061056_396457_745F80D2 X-CRM114-Status: GOOD ( 12.85 ) 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: kernel-team@android.com, Suzuki K Poulose , Catalin Marinas , linux-kernel@vger.kernel.org, James Morse , linux-arm-kernel@lists.infradead.org, Marc Zyngier , Tejun Heo , Dennis Zhou , Will Deacon , kvmarm@lists.cs.columbia.edu, Julien Thierry 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 Tue, 22 Sep 2020, David Brazdil wrote: > Introduce '.hyp.data..percpu' as part of ongoing effort to make nVHE > hyp code self-contained and independent of the rest of the kernel. The percpu subsystems point is to enable the use of special hardware instructions that can perform address calculation and a memory operation in one interruptible instruction. This is in particular useful to avoid higher overhead for memory management related counters because preempt disable/enable etc can be avoided. ARM cannot do that and thus has a LC/SC loop. This is a patchset for ARM64 so its not clear to me what kind of advantage there would be against a simple implementation that does a regular fetch from a base address with an offset. > Main benefits: > * independent nVHE per-CPU data section that can be unmapped from host, > * more robust linking of nVHE hyp code, > * no need for hyp-specific macros to access per-CPU variables. Maybe simply don't use percpu variables for your arm code? Those pointers to data will be much more indepedent of the rest of the kernel and allow a much higher degree of being self-contained. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel