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=-2.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 B230AC3A5A3 for ; Tue, 27 Aug 2019 08:16:00 +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 896D5206BA for ; Tue, 27 Aug 2019 08:16:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="Wd1Fzn/T" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 896D5206BA Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org 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=lMhmWJ/BVVuWw9e/8OA3ch2K+QO+Hw0RQ+rXwuWmOGg=; b=Wd1Fzn/TvbSgN0 Y0QXax1PlATMfy2MG1zNEbQRoIhLO0agvyJXz0x+Yiji4f3ujW1jwP8k8MP2oV0ksNgCfWIuARp1f s/hPs4DXWnDc7HCOYcSJTLf9or3UcInryOog0rSssbm/PD92jZVosE9wY6vJXIt7hzZk8DdBA3omC CBVOVJ42c8CNUHs+U98x3vtqoWozTW7MSJOCUGVqfPoOkzUII8Npsvct21WcBfSi9b4C0fDztMj1V S9fac/qLV2YxbxXfvFLTYIYWYLWDbfCz1pe912iw8AnDTrkqcpVZeR/6p0NFDOTqMeJdZQkPqUpXk xD5yl98VBRrQxQFLye5g==; 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 1i2Wdu-0005ZA-02; Tue, 27 Aug 2019 08:15:54 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1i2Wdo-0005Xl-I4; Tue, 27 Aug 2019 08:15:50 +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 A6A82337; Tue, 27 Aug 2019 01:15:45 -0700 (PDT) Received: from [10.1.197.61] (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 61C483F246; Tue, 27 Aug 2019 01:15:44 -0700 (PDT) Subject: Re: [PATCH v1 0/6] Allow kexec reboot for GICv3 and device tree To: Pavel Tatashin References: <20190826190056.27854-1-pasha.tatashin@soleen.com> <20190826201313.246208e9@why> From: Marc Zyngier Organization: Approximate Message-ID: Date: Tue, 27 Aug 2019 09:15:43 +0100 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190827_011548_686193_D5C22C82 X-CRM114-Status: GOOD ( 22.41 ) 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: Sasha Levin , Mark Rutland , Vladimir Murzin , kexec mailing list , James Morris , LKML , James Morse , Linux ARM 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 26/08/2019 22:25, Pavel Tatashin wrote: > On Mon, Aug 26, 2019 at 3:13 PM Marc Zyngier wrote: >> >> On Mon, 26 Aug 2019 15:00:50 -0400 >> Pavel Tatashin wrote: >> >>> Marc Zyngier added the support for kexec and GICv3 for EFI based systems. >>> However, it is still not possible todo on systems with device trees. >>> >>> Here is EFI fixes from Marc: >>> https://lore.kernel.org/lkml/20180921195954.21574-1-marc.zyngier@arm.com >>> >>> For Device Tree variant: lets allow reserve a memory region in interrupt >>> controller node, and use this property to allocate interrupt tables. >> >> There is no such thing as a "device tree variant". As long as your >> bootloader implements EFI, everything will work correctly, whether >> you're using DT, ACPI, or the anything else. >> >> This already works today, without any need to add anything to the >> kernel (I have systems using EDK II and u-boot, both implementing EFI, >> and I'm able to kexec without any issue). If your bootloader doesn't >> support EFI, here's a good opportunity to implement it! > > Hi Marc, > > Thank you very much for looking at this work. > > Running Linux without EFI is common, and there are scenarios which > make it appropriate. As I understand most of embedded linux do not > have EFI enabled, and thus I do not see a reason why we would not > support a first class feature of Linux (kexec) on non-EFI bootloaders. Define "most". All the arm64 systems I have around (and trust me, that's quite a number of them) can either use u-boot, which has more than enough EFI support to use this functionality, or use EDK-II natively. > We (Microsoft) have a small highly secure device with a high uptime > requirement. The device also has PCIe and thus GICv3. The update for PCIe doesn't imply GICv3 at all. > this device relies on kexec. For a number of reasons, it was decided > to use U-Boot and Linux without EFI enabled. One of those reasons is > to improve boot performance, enabling EFI in U-Boot alone reduces the > boot performance by half a second. Our total reboot budget is under a > second which makes that half a second unacceptable. Also, adding EFI > support to kernel increases its size and there are security > implications from enabling more code both in U-Boot and Linux. You're are missing the point. kexec with EFI has 0 overhead (no non-kernel EFI code gets executed), doesn't impact your time budget, and only relies on a single in-memory table. This can be pretty trivially provided by the dumbest EFI shim. All you are describing above is a set of self imposed limitations in your bootloader, which you are fully in control of. So instead of reinventing a square wheel, I suggest you adopt the existing implementation. Another reason not to do this is interoperability: I want to be able to kexec whatever Linux kernel I want, without having to cope with all flavours of the same functionality. Effectively, the EFI table is a private ABI between two Linux kernels. We're not changing it. M. -- Jazz is not dead, it just smells funny... _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel