From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751670AbbCIX0O (ORCPT ); Mon, 9 Mar 2015 19:26:14 -0400 Received: from mga14.intel.com ([192.55.52.115]:10242 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751016AbbCIX0L (ORCPT ); Mon, 9 Mar 2015 19:26:11 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.11,371,1422950400"; d="scan'208";a="464867994" Message-ID: <54FE2C0B.10209@linux.intel.com> Date: Tue, 10 Mar 2015 07:26:03 +0800 From: "Li, Aubrey" User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-Version: 1.0 To: Ingo Molnar CC: Arjan van de Ven , Borislav Petkov , "alan@linux.intel.com" , "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , "Rafael J. Wysocki" , Len.Brown@intel.com, x86@kernel.org, LKML Subject: Re: [PATCH] x86: Bypass legacy PIC and PIT on ACPI hardware reduced platform References: <20150304050858.GB5158@gmail.com> <54F69774.2050400@linux.intel.com> <20150304053106.GA3701@gmail.com> <54F6A08B.2010105@linux.intel.com> <20150304073717.GA11736@gmail.com> <54F6C59C.706@linux.intel.com> <20150304095011.GH3233@pd.tnic> <54F71888.4040608@linux.intel.com> <20150304201102.GA6530@gmail.com> <54F83A61.3090906@linux.intel.com> <20150305113641.GB23046@gmail.com> <54F84F3A.8080902@linux.intel.com> In-Reply-To: <54F84F3A.8080902@linux.intel.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2015/3/5 20:42, Li, Aubrey wrote: > On 2015/3/5 19:36, Ingo Molnar wrote: >> >> * Li, Aubrey wrote: >> >>> On 2015/3/5 4:11, Ingo Molnar wrote: >>>> >>>> * Arjan van de Ven wrote: >>>> >>>>> On 3/4/2015 1:50 AM, Borislav Petkov wrote: >>>>>> On Wed, Mar 04, 2015 at 12:43:08AM -0800, Arjan van de Ven wrote: >>>>>>>> >>>>>>>> Using 'acpi_gbl_reduced_hardware' flag outside the ACPI code >>>>>>>> is a mistake. >>>>>>> >>>>>>> ideally, the presence of that flag in the firmware table will clear/set more global settings, >>>>>>> for example, having that flag should cause the 8042 input code to not probe for the 8042. >>>>>>> >>>>>>> for interrupts, there really ought to be a "apic first/only" mode, which is then used on >>>>>>> all modern systems (not just hw reduced). >>>>>> >>>>>> Do we need some sort of platform-specific querying interfaces now too, >>>>>> similar to cpu_has()? I.e., platform_has()... >>>>>> >>>>>> if (platform_has(X86_PLATFORM_REDUCED_HW)) >>>>>> do stuff.. >>>>> >>>>> more like >>>>> >>>>> platform_has(X86_PLATFORM_PIT) >>>>> >>>>> etc, one for each legacy io item >>>> >>>> Precisely. The main problem is the generic, 'lumps everything >>>> together' nature of the acpi_gbl_reduced_hardware flag. >>>> >>>> (Like the big kernel lock lumped together all sorts of locking rules >>>> and semantics.) >>>> >>>> Properly split out, feature-ish or driver-ish interfaces for PIT and >>>> other legacy details are the proper approach to 'turn them off'. >>>> >>>> - x86_platform is a function pointer driven, driver-ish interface. >>>> >>>> - platform_has(X86_PLATFORM_IT) is a flag driven, feature-flag-ish >>>> interface. >>>> >>>> Both are fine - for something as separate as the PIT (or the PIC) >>>> it might make more sense to go towards a 'driver' interface >>>> though, as modern drivers are (and will be) much different from >>>> the legacy PIT. >>>> >>>> Whichever method is used, low level platforms can just switch them >>>> on/off in their enumeration/detection routines, while the generic >>>> code will have them enabled by default. >>> >>> Whichever method is used, we will face a problem how to determine >>> PIT exists or not. >>> >>> When we enabled Bay Trail-T platform at the beginning, we were >>> trying to make the code as generic as possible, and it works >>> properly up to now. So we don't have a SUBARCH like >>> X86_SUBARCH_INTEL_MID to use the platform specific functions. And >>> for now I'm not quite sure it's a good idea to create one. >>> >>> If we make it as a flag driven, I don't know there is a flag in >>> firmware better than ACPI HW reduced flag(Of course it's not good >>> enough to cover all the cases). Or if we want to use platform info >>> to turn on/off this flag, we'll have to maintain a platform list, >>> which may be longer and more complicated than worth doing that. >> >> Well, it's not nearly so difficult, because you already have a >> platform flag: acpi_gbl_reduced_hardware. >> >> What I object against is to infest generic codepaths with unreadable, >> unrobust crap like: >> >> + if (acpi_gbl_reduced_hardware) { >> + pr_info("Using NULL legacy PIC\n"); >> + legacy_pic = &null_legacy_pic; >> + } else >> + legacy_pic->init(0); >> >> To solve that, add a small (early) init function (say >> 'x86_reduced_hw_init()') that sets up the right driver >> selections if acpi_gbl_reduced_hardware is set: >> >> - in x86_reduced_hw_init() set 'legacy_pic' to 'null_legacy_pic' >> >> - clean up 'global_clock_event' handling: instead of a global >> variable, move its management into x86_platform_ops::get_clockevent() >> and set the method to hpet/pit/abp/etc. specific handlers that >> return the right clockevent device. >> >> - in your x86_reduced_hw_init() function add the hpet clockevent >> device to x86_platform_ops::get_clockevent, overriding the default >> PIT. >> how about this one? diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c index b9e30da..70955d6 100644 --- a/arch/x86/kernel/acpi/boot.c +++ b/arch/x86/kernel/acpi/boot.c @@ -1541,6 +1541,16 @@ int __init early_acpi_boot_init(void) */ early_acpi_process_madt(); + /* + * Override x86_init functions and bypass legacy pic + * in hardware-reduced ACPI mode + */ + if (acpi_gbl_reduced_hardware) { + x86_init.timers.timer_init = x86_init_noop; + x86_init.irqs.pre_vector_init = x86_init_noop; + legacy_pic = &null_legacy_pic; + } + return 0; } > >> - in x86_reduced_hw_init() set pm_power_off. >> >> - set 'reboot_type' and remove the acpi_gbl_reduced_hardware hack >> from efi_reboot_required(). >> > I'll do more investigation above items but I want to leave at least > these two as the quirk today unless I am convinced I can do that because > from my understanding, UEFI runtime services should not be supported in > reduced hw mode. > If the above makes sense, I'll send poweroff and reboot change together in a seperate patch. Thanks, -Aubrey