From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754366AbbAUPzf (ORCPT ); Wed, 21 Jan 2015 10:55:35 -0500 Received: from www.xora.org.uk ([80.68.91.202]:38588 "EHLO xora.vm.bytemark.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750868AbbAUPz0 (ORCPT ); Wed, 21 Jan 2015 10:55:26 -0500 Date: Wed, 21 Jan 2015 15:56:41 +0000 From: Graeme Gregory To: Catalin Marinas Cc: Jon Masters , Stefano Stabellini , "hanjun.guo@linaro.org" , Mark Rutland , "grant.likely@linaro.org" , Ard Biesheuvel , "linaro-acpi@lists.linaro.org" , Will Deacon , "wangyijing@huawei.com" , Rob Herring , Lorenzo Pieralisi , Al Stone , Timur Tabi , "linux-acpi@vger.kernel.org" , Charles Garcia-Tobin , "phoenix.liyi@huawei.com" , Robert Richter , Jason Cooper , Arnd Bergmann , Marc Zyngier , Mark Brown , Bjorn Helgaas , "linux-arm-kernel@lists.infradead.org" , "graeme.gregory@linaro.org" , Randy Dunlap , "Rafael J. Wysocki" , "linux-kernel@vger.kernel.org" , "suravee.suthikulpanit@amd.com" , Sudeep Holla , Olof Johansson , "christoffer.dall@linaro.org" , "parth.dixit@linaro.org" , Leif Lindholm Subject: Re: [PATCH v7 04/17] ARM64 / ACPI: Introduce early_param for "acpi" and pass acpi=force to enable ACPI Message-ID: <20150121155641.GE6858@xora-yoga-13.xora.org.uk> References: <20150119135144.GI11835@e104818-lin.cambridge.arm.com> <20150119151350.21B65C40948@trevor.secretlab.ca> <54BD3803.6020307@redhat.com> <20150119175233.GK11835@e104818-lin.cambridge.arm.com> <20150119180122.GJ21553@leverpostej> <54BE1FEA.5040109@linaro.org> <20150121152326.GD6358@e104818-lin.cambridge.arm.com> <54BFC5F0.3020500@redhat.com> <20150121154243.GE6358@e104818-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150121154243.GE6358@e104818-lin.cambridge.arm.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 21, 2015 at 03:42:43PM +0000, Catalin Marinas wrote: > On Wed, Jan 21, 2015 at 03:29:52PM +0000, Jon Masters wrote: > > On 01/21/2015 10:23 AM, Catalin Marinas wrote: > > > I have some questions for the ACPI and EFI folk: > > > > > > 1. When booting with ACPI, are the EFI run-time services required for > > > anything? If yes, Xen may have a bigger problem > > > > Yes. At least for some things. For example, installing an Operating > > System would require that you make runtime services calls to set the > > BootOrder/BootNext variables, and so on. Further, we use the GetTime > > service and EFI based reboot to avoid having special drivers. I had > > those added to SBBR as requirements for that reason. > > So what would a kexec'ed kernel do here? Or we usually expect it to be > short lived and doesn't need reboot, nor GetTime. > > Xen is slightly more problematic but I wonder whether it could run a > (paravirtualised) UEFI. > > > > 2. Could a boot loader (either kernel doing kexec or Xen) emulate the > > > EFI system/config tables and still make them useful to the kernel but > > > without EFI_BOOT or EFI_RUNTIME_SERVICES? > > > > Yes. But again, without the other required pieces (including the > > services function pointers in the systab which are required) you'd crash > > soon after boot trying to make those calls. > > My point was whether you can still pass information like RSDP address > via EFI tables but explicitly disable runtime services so that the > kernel won't try to make such calls (and crash). > There is no specific dependency from ACPI->EFI its just the only current method defind to get the RSDP pointer. It would work just as well getting the pointer from /chosen/ if we just pick a node and document it for Xen/kexec/other usage. We were running ACPI on machine from u-boot doing exactly this for a long time. Graeme