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,DKIM_VALID_AU,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 394FFC388F9 for ; Wed, 11 Nov 2020 12:46:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CEDAE2068D for ; Wed, 11 Nov 2020 12:46:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="r9nWEq3/" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726628AbgKKMqf (ORCPT ); Wed, 11 Nov 2020 07:46:35 -0500 Received: from mail.kernel.org ([198.145.29.99]:48938 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725908AbgKKMqe (ORCPT ); Wed, 11 Nov 2020 07:46:34 -0500 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id D2AA520709; Wed, 11 Nov 2020 12:46:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605098793; bh=fgvFar5VH6U4VmS5tTBAQ11UfAbcAq37UA/xmP7e4uI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=r9nWEq3/jfTwQEjDuIXAGQ3H5G3m3fz1i1Uank6++ovoprns/8F8c+AJfmJKnfkV7 U9NlWyNw0S5q4V2xcpf3b2+tlqT2T4LDiaqsi1VnqngsXR8NZmG4TrZwTzJ7CAHd82 DHwKVfdZtvolrjK4/t4Wre1aIEKeFreUOxIC7ckM= Received: from disco-boy.misterjones.org ([51.254.78.96] helo=www.loen.fr) by disco-boy.misterjones.org with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.94) (envelope-from ) id 1kcpWA-009lDZ-KI; Wed, 11 Nov 2020 12:46:30 +0000 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Wed, 11 Nov 2020 12:46:30 +0000 From: Marc Zyngier To: David Brazdil Cc: kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, James Morse , Julien Thierry , Suzuki K Poulose , Catalin Marinas , Will Deacon , Dennis Zhou , Tejun Heo , Christoph Lameter , Mark Rutland , Lorenzo Pieralisi , Quentin Perret , Andrew Scull , Andrew Walbran , kernel-team@android.com Subject: Re: [PATCH v1 06/24] kvm: arm64: Support per_cpu_ptr in nVHE hyp code In-Reply-To: <20201111123222.ooevu6nryu3ncphv@google.com> References: <20201109113233.9012-1-dbrazdil@google.com> <20201109113233.9012-7-dbrazdil@google.com> <20201111123222.ooevu6nryu3ncphv@google.com> User-Agent: Roundcube Webmail/1.4.9 Message-ID: <52b47a4284aaff2e198385ef9acbe01f@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: dbrazdil@google.com, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, catalin.marinas@arm.com, will@kernel.org, dennis@kernel.org, tj@kernel.org, cl@linux.com, mark.rutland@arm.com, lorenzo.pieralisi@arm.com, qperret@google.com, ascull@google.com, qwandor@google.com, kernel-team@android.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020-11-11 12:32, David Brazdil wrote: >> > + >> > + cpu_base_array = kern_hyp_va(&kvm_arm_hyp_percpu_base[0]); >> >> There is no guarantee that this will not generate a PC relative >> addressing, resulting in kern_hyp_va() being applied twice. >> >> Consider using hyp_symbol_addr() instead, which always does the right >> by forcing a PC relative addressing and not subsequently mangling >> the address. >> >> > + this_cpu_base = kern_hyp_va(cpu_base_array[cpu]); >> > + return this_cpu_base - (unsigned long)&__per_cpu_start; >> >> And this is the opposite case: if the compiler generates an absolute >> address, you're toast. Yes, this is just as unlikely, but hey... >> Same remedy should apply. > > Good point, and I'll probably keep forgetting about this in the future. > Now > that all .hyp.text is only executed under hyp page tables, should we > start > thinking about fixing up the relocations? Why not, if you can deal with the hypervisor text being mapped at a random location, and make sure that the kernel doesn't process the relocations for you. This would certainly save us a lot of runtime offsetting (which I'm adding to in a separate series). M. -- Jazz is not dead. It just smells funny...