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=-1.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, URIBL_BLOCKED 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 E1E61C282D9 for ; Thu, 31 Jan 2019 16:22:56 +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 ACE262085B for ; Thu, 31 Jan 2019 16:22:56 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="tm9H/Hzr" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org ACE262085B 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:Date: Message-ID:From:References:To:Subject:Reply-To:Content-ID:Content-Description :Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=wAPlaC3tai11X1NRqIevxvdL34TvW37PMr9Ku0IaQPU=; b=tm9H/HzrQFthq4 s1xUlS5i78BEgLVi4FNBZXk+Z8ysne+gYCZSbeUbFiOEygciHeGTY7m3bmi+hBndgezisy8pc2rF8 9cMUxWkGU1gG+goFD0ID5t5Yq+k3QUNlGh6gg+FbZC2ZYc/EKa3/IL9e1VCX1J9XcRwnvsDayJfDZ wy0PZNZAGUMCVlxtrwb863O5T3zpVJYHt6+XYFm+8v3PBofdUvJSRLU61zaT/Zntc2FP+M0LUWXK8 zOPM+yHHd6p+28S5usT5LD/inl3wGOUpQDgt49l36ZHhHh22vbX86VcWedYx6GrVjncNQrXsV9Wgp sTgtJctkjZQH40aiwmcw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gpF76-0002Th-Ls; Thu, 31 Jan 2019 16:22:52 +0000 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70] helo=foss.arm.com) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gpF42-0006c0-Iy for linux-arm-kernel@lists.infradead.org; Thu, 31 Jan 2019 16:20:31 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 22C3A80D; Thu, 31 Jan 2019 08:19:39 -0800 (PST) Received: from [10.1.196.105] (eglon.cambridge.arm.com [10.1.196.105]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 759CB3F557; Thu, 31 Jan 2019 08:19:37 -0800 (PST) Subject: Re: [PATCH v4 3/6] arm64/kvm: add a userspace option to enable pointer authentication To: Amit Daniel Kachhap References: <1545119810-12182-1-git-send-email-amit.kachhap@arm.com> <1545119810-12182-4-git-send-email-amit.kachhap@arm.com> <49474d5f-6f4e-b57d-4b45-94c16d85136c@arm.com> From: James Morse Message-ID: <3936d9fd-1e3f-0437-e866-edf2d9cbf797@arm.com> Date: Thu, 31 Jan 2019 16:19:35 +0000 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-GB X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190131_081943_258581_4DFF614C X-CRM114-Status: GOOD ( 15.45 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Marc Zyngier , Catalin Marinas , Will Deacon , linux-kernel@vger.kernel.org, Kristina Martsenko , Dave Martin , Ramana Radhakrishnan , kvmarm@lists.cs.columbia.edu, LAK 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 Hi Amit, On 09/01/2019 10:13, Amit Daniel Kachhap wrote: > On Sat, Jan 5, 2019 at 12:05 AM James Morse wrote: >> On 18/12/2018 07:56, Amit Daniel Kachhap wrote: >>> This feature will allow the KVM guest to allow the handling of >>> pointer authentication instructions or to treat them as undefined >>> if not set. It uses the existing vcpu API KVM_ARM_VCPU_INIT to >>> supply this parameter instead of creating a new API. >>> >>> A new register is not created to pass this parameter via >>> SET/GET_ONE_REG interface as just a flag (KVM_ARM_VCPU_PTRAUTH) >>> supplied is enough to select this feature. >> >> What is the motivation for doing this? Doesn't ptrauth 'just' need turning on? >> It doesn't need additional setup to be useable, or rely on some qemu support to >> work properly. There isn't any hidden state that can't be migrated in the usual way. >> Is it just because we don't want to commit to the ABI? > This allows migration of guest to non pointer authenticated supported > systems and hides the extra ptrauth registers. The MIDR already has to match, so the hardware must be the same. I guess this lets us hide the new feature so old-guests can migrate to a new-kernel without a write to the id registers failing. > Basically this suggestion was given by Christoffer > (https://lore.kernel.org/lkml/20180206123847.GY21802@cbox/). Ah, Christoffer asked for it, that's reason enough! Thanks, James _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel