Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752092AbbBGGv7 (ORCPT ); Sat, 7 Feb 2015 01:51:59 -0500 Received: from mail-pd0-f171.google.com ([209.85.192.171]:37512 "EHLO mail-pd0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751102AbbBGGv4 (ORCPT ); Sat, 7 Feb 2015 01:51:56 -0500 Message-ID: <54D5B601.60807@linaro.org> Date: Sat, 07 Feb 2015 14:51:45 +0800 From: Hanjun Guo User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 MIME-Version: 1.0 To: Ard Biesheuvel CC: G Gregory , Mark Rutland , Leif Lindholm , Mark Langsdorf , "linaro-acpi@lists.linaro.org" , Catalin Marinas , Will Deacon , "wangyijing@huawei.com" , Rob Herring , Lorenzo Pieralisi , Jonathan Corbet , Timur Tabi , Daniel Lezcano , "linux-acpi@vger.kernel.org" , "grant.likely@linaro.org" , Charles Garcia-Tobin , "phoenix.liyi@huawei.com" , Robert Richter , Jason Cooper , Arnd Bergmann , Marc Zyngier , "jcm@redhat.com" , Mark Brown , Bjorn Helgaas , "linux-arm-kernel@lists.infradead.org" , Matt Fleming , Ashwin Chaugule , Randy Dunlap , "Rafael J. Wysocki" , "linux-kernel@vger.kernel.org" , "suravee.suthikulpanit@amd.com" , Sudeep Holla , Olof Johansson Subject: Re: [PATCH v8 08/21] dt / chosen: Add linux,uefi-stub-generated-dtb property References: <1422881149-8177-1-git-send-email-hanjun.guo@linaro.org> <1422881149-8177-9-git-send-email-hanjun.guo@linaro.org> <20150202134033.GR4278@bivouac.eciton.net> <20150202135051.GA3825@xora-haswell.xora.org.uk> <20150202163253.GG21175@leverpostej> <54D5884A.6050009@linaro.org> In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3251 Lines: 82 On 2015年02月07日 13:03, Ard Biesheuvel wrote: > On 7 February 2015 at 03:36, Hanjun Guo wrote: >> On 2015年02月06日 18:34, G Gregory wrote: >> [...] >> >>>>>>> >>>>>>> -------------------------------------------------------------------------------- >>>>>>> linux,uefi-stub-kern-ver | string | Copy of linux_banner from >>>>>>> build. >>>>>>> >>>>>>> -------------------------------------------------------------------------------- >>>>>>> +linux,uefi-stub-generated-dtb | bool | Indication for no DTB >>>>>>> provided by >>>>>>> + | | firmware. >>>>>>> >>>>>>> +-------------------------------------------------------------------------------- >>>>>> >>>>>> >>>>>> Apologies for the late bikeshedding, but the discussion on this topic >>>>>> previsously was lively enough that I thought I'd let it die down a bit >>>>>> before seeing if I had anything to add. >>>>>> >>>>>> That, and I just realised something: >>>>>> One alternative to this added DT entry is that we could treat the >>>>>> absence of a registered UEFI configuration table as the indication >>>>>> that no HW description was provided from firmware, since the stub does >>>>>> not call InstallConfigurationTable() on the DT it generates. This does >>>>>> move the ability to detect to after efi_init(), but this should be >>>>>> fine for ACPI-purposes. >>>>>> >>>>> That would not work as expected in the kexec/Xen use case though as they >>>>> may genuinely boot with DT from an ACPI host without UEFI. >>>> >>>> >>>> I'm a little concerned by this case. How do we intend to pass stuff from >>>> Xen to the kernel in this case? When we initially discussed the stub >>>> prior to merging, we weren't quite sure if ACPI without UEFI was >>>> entirely safe. >>>> >>>> The linux,uefi-stub-kern-ver property was originally intended as a >>>> sanity-check feature to ensure nothing (including Xen) masqueraded as >>>> the stub, but for some reason the actual sanity check was never >>>> implemented. >>>> >>>>>> If that is deemed undesirable, I would still prefer Catalin's >>>>>> suggested name ("linux,bare-dtb"), which describes the state rather >>>>>> than the route we took to get there. >>>>>> >>>>> I agree. >>>> >>>> >>>> I guess this would be ok, though it would be nice to know which agent >>>> generated the DTB. >>>> >>> >>> The most obvious scheme then is >>> >>> linux,bare-dtb = "uefi-stub"; >>> >>> otherwise we generate a new binding for every component in the boot path. >> >> >> Leif, Mark, any comments on this? >> > > As far as I remember, we did not finalize the decision to go with a > stub generated property instead of some other means to infer that the > device tree is not suitable for booting and ACPI should be preferred. > > We will be discussing the 'stub<->kernel interface as a boot protocol' > topic this week at Connect, so let's discuss it in that context before > signing off on patches like these. OK, see you guys in Hongkong. Thanks Hanjun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/