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=-5.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 0B2A1C433DF for ; Wed, 14 Oct 2020 01:06:51 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (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 9F0CA208B3 for ; Wed, 14 Oct 2020 01:06:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="hChKhc0D" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9F0CA208B3 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.6422.17110 (Exim 4.92) (envelope-from ) id 1kSVFP-00027U-Vf; Wed, 14 Oct 2020 01:06:31 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 6422.17110; Wed, 14 Oct 2020 01:06:31 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kSVFP-00027K-SG; Wed, 14 Oct 2020 01:06:31 +0000 Received: by outflank-mailman (input) for mailman id 6422; Wed, 14 Oct 2020 01:06:30 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kSVFN-00027F-Vd for xen-devel@lists.xenproject.org; Wed, 14 Oct 2020 01:06:30 +0000 Received: from mail.kernel.org (unknown [198.145.29.99]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id eb69429e-fdaa-497c-9685-157bef0fd2eb; Wed, 14 Oct 2020 01:06:28 +0000 (UTC) Received: from sstabellini-ThinkPad-T480s (c-24-130-65-46.hsd1.ca.comcast.net [24.130.65.46]) (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 13736208B3; Wed, 14 Oct 2020 01:06:27 +0000 (UTC) Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kSVFN-00027F-Vd for xen-devel@lists.xenproject.org; Wed, 14 Oct 2020 01:06:30 +0000 X-Inumbo-ID: eb69429e-fdaa-497c-9685-157bef0fd2eb Received: from mail.kernel.org (unknown [198.145.29.99]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id eb69429e-fdaa-497c-9685-157bef0fd2eb; Wed, 14 Oct 2020 01:06:28 +0000 (UTC) Received: from sstabellini-ThinkPad-T480s (c-24-130-65-46.hsd1.ca.comcast.net [24.130.65.46]) (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 13736208B3; Wed, 14 Oct 2020 01:06:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1602637587; bh=oJhlGVtF1Tk5FO3i6heiukaqcfG80pU4yQtavGGC3OU=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=hChKhc0Ds+AoHI3nIdnZUO+zSc8AvIY2mkuqkK6RlOdHUOQ3ELufx1d9mvESXB7qu kG8Qqr3GuvKkhnAIVMNWOHTASlABpInTPLvuhK8dFHgWwdbFj/5ukbdnIpjWC5NvnO 1Xr2A+BSjS9vqjB0qmzCiWS2eWptnmW8TX141mWA= Date: Tue, 13 Oct 2020 18:06:26 -0700 (PDT) From: Stefano Stabellini X-X-Sender: sstabellini@sstabellini-ThinkPad-T480s To: Elliott Mitchell cc: Stefano Stabellini , Julien Grall , Masami Hiramatsu , xen-devel@lists.xenproject.org, Alex Benn??e , bertrand.marquis@arm.com, andre.przywara@arm.com, Julien Grall , Volodymyr Babchuk Subject: Re: [PATCH 0/4] xen/arm: Unbreak ACPI In-Reply-To: <20201012213451.GA89158@mattapan.m5p.com> Message-ID: References: <20200926205542.9261-1-julien@xen.org> <1a7b5a14-7d21-b067-a80b-27d963f9798a@xen.org> <20201012213451.GA89158@mattapan.m5p.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII On Mon, 12 Oct 2020, Elliott Mitchell wrote: > On Mon, Oct 12, 2020 at 12:02:14PM -0700, Stefano Stabellini wrote: > > On Sat, 10 Oct 2020, Julien Grall wrote: > > > Therefore, I think the code should not try to find the STAO. Instead, it > > > should check whether the SPCR table is present. > > > > Yes, that makes sense, but that brings me to the next question. > > > > SPCR seems to be required by SBBR, however, Masami wrote that he could > > boot on a system without SPCR, which gets me very confused for two > > reasons: > > > > 1) Why there is no SPCR? Isn't it supposed to be mandatory? Is it > > because there no UART on Masami's system? > > I'm on different hardware, but some folks have setup Tianocore for it. > According to Documentation/arm64/acpi_object_usage.rst, > "Required: DSDT, FADT, GTDT, MADT, MCFG, RSDP, SPCR, XSDT". Yet when > booting a Linux kernel directly on the hardware it lists APIC, BGRT, > CSRT, DSDT, DBG2, FACP, GTDT, PPTT, RSDP, and XSDT. > > I don't know whether Linux's ACPI code omits mention of some required > tables and merely panics if they're absent. Yet I'm speculating the list > of required tables has shrunk, SPCR is no longer required, and the > documentation is out of date. Perhaps SPCR was required in early Linux > ACPI implementations, but more recent ones removed that requirement? I have just checked and SPCR is still a mandatory table in the latest SBBR specification. It is probably one of those cases where the firmware claims to be SBBR compliant, but it is not, and it happens to work with Linux.