Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S970989AbdDTSJf (ORCPT ); Thu, 20 Apr 2017 14:09:35 -0400 Received: from foss.arm.com ([217.140.101.70]:57698 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S970605AbdDTSJd (ORCPT ); Thu, 20 Apr 2017 14:09:33 -0400 Subject: Re: [PATCH] arm64: xen: Implement EFI reset_system callback To: Juergen Gross , Stefano Stabellini References: <20170405181417.15985-1-julien.grall@arm.com> <3f6f5853-cd08-8afc-f71a-b0c1545c7564@arm.com> <20170406142710.GE4372@olila.local.net-space.pl> <20170406152040.GH4372@olila.local.net-space.pl> <20170406160653.GJ4372@olila.local.net-space.pl> <20170406164309.GM4372@olila.local.net-space.pl> Cc: Daniel Kiper , Boris Ostrovsky , xen-devel@lists.xen.org, linux-arm-kernel@lists.infradead.org, "linux-kernel@vger.kernel.org" , Mark Rutland , ard.biesheuvel@linaro.org, linux-efi@vger.kernel.org, matt@codeblueprint.co.uk From: Julien Grall Message-ID: <66b377bd-999f-9010-8257-95f663f4ebd2@arm.com> Date: Thu, 20 Apr 2017 19:09:29 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4800 Lines: 114 Hi, On 18/04/17 19:51, Juergen Gross wrote: > On 18/04/17 20:46, Stefano Stabellini wrote: >> On Tue, 18 Apr 2017, Juergen Gross wrote: >>> On 18/04/17 20:37, Stefano Stabellini wrote: >>>> On Thu, 6 Apr 2017, Juergen Gross wrote: >>>>> On 06/04/17 18:43, Daniel Kiper wrote: >>>>>> On Thu, Apr 06, 2017 at 06:22:44PM +0200, Juergen Gross wrote: >>>>>>> On 06/04/17 18:06, Daniel Kiper wrote: >>>>>>>> Hi Julien, >>>>>>>> >>>>>>>> On Thu, Apr 06, 2017 at 04:39:13PM +0100, Julien Grall wrote: >>>>>>>>> Hi Daniel, >>>>>>>>> >>>>>>>>> On 06/04/17 16:20, Daniel Kiper wrote: >>>>>>>>>> On Thu, Apr 06, 2017 at 04:38:24PM +0200, Juergen Gross wrote: >>>>>>>>>>> On 06/04/17 16:27, Daniel Kiper wrote: >>>>>>>>>>>> On Thu, Apr 06, 2017 at 09:32:32AM +0100, Julien Grall wrote: >>>>>>>>>>>>> Hi Juergen, >>>>>>>>>>>>> >>>>>>>>>>>>> On 06/04/17 07:23, Juergen Gross wrote: >>>>>>>>>>>>>> On 05/04/17 21:49, Boris Ostrovsky wrote: >>>>>>>>>>>>>>> On 04/05/2017 02:14 PM, Julien Grall wrote: >>>>>>>>>>>>>>>> The x86 code has theoritically a similar issue, altought EFI does not >>>>>>>>>>>>>>>> seem to be the preferred method. I have left it unimplemented on x86 and >>>>>>>>>>>>>>>> CCed Linux Xen x86 maintainers to know their view here. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> (+Daniel) >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> This could be a problem for x86 as well, at least theoretically. >>>>>>>>>>>>>>> xen_machine_power_off() may call pm_power_off(), which is efi.reset_system. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> So I think we should have a similar routine there. >>>>>>>>>>>>>> >>>>>>>>>>>>>> +1 >>>>>>>>>>>>>> >>>>>>>>>>>>>> I don't see any problem with such a routine added, in contrast to >>>>>>>>>>>>>> potential "reboots" instead of power off without it. >>>>>>>>>>>>>> >>>>>>>>>>>>>> So I think this dummy xen_efi_reset_system() should be added to >>>>>>>>>>>>>> drivers/xen/efi.c instead. >>>>>>>>>>>>> >>>>>>>>>>>>> I will resend the patch during day with xen_efi_reset_system moved >>>>>>>>>>>>> to common code and implement the x86 counterpart (thought, I will >>>>>>>>>>>>> not be able to test it). >>>>>>>>>>>> >>>>>>>>>>>> I think that this is ARM specific issue. On x86 machine_restart() calls >>>>>>>>>>>> xen_restart(). Hence, everything works. So, I think that it should be >>>>>>>>>>>> fixed only for ARM. Anyway, please CC me when you send a patch. >>>>>>>>>>> >>>>>>>>>>> What about xen_machine_power_off() (as stated in Boris' mail)? >>>>>>>>>> >>>>>>>>>> Guys what do you think about that: >>>>>>>>>> >>>>>>>>>> --- a/drivers/firmware/efi/reboot.c >>>>>>>>>> +++ b/drivers/firmware/efi/reboot.c >>>>>>>>>> @@ -55,7 +55,7 @@ static void efi_power_off(void) >>>>>>>>>> >>>>>>>>>> static int __init efi_shutdown_init(void) >>>>>>>>>> { >>>>>>>>>> - if (!efi_enabled(EFI_RUNTIME_SERVICES)) >>>>>>>>>> + if (!efi_enabled(EFI_RUNTIME_SERVICES) || efi_enabled(EFI_PARAVIRT)) >>>>>>>>>> return -ENODEV; >>>>>>>>>> >>>>>>>>>> if (efi_poweroff_required()) >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> Julien, for ARM64 please take a look at arch/arm64/kernel/efi.c:efi_poweroff_required(void). >>>>>>>>>> >>>>>>>>>> I hope that tweaks for both files should solve our problem. >>>>>>>>> >>>>>>>>> This sounds good for power off (I haven't tried to power off DOM0 >>>>>>>>> yet). But this will not solve the restart problem (see >>>>>>>>> machine_restart in arch/arm64/kernel/process.c) which call directly >>>>>>>>> efi_reboot. >>>>>>>> >>>>>>>> Hmmm... It seems to me that efi.reset_system override with empty function >>>>>>>> in arch/arm/xen/efi.c is the best solution. So, I see three patches here. >>>>>>>> One for drivers/firmware/efi/reboot.c, one for arch/arm/xen/efi.c and one >>>>>>>> for arch/arm64/kernel/efi.c. Does it make sense? >>>>>>> >>>>>>> I still think the empty function should be in drivers/xen/efi.c and we >>>>>>> should use it in arch/x86/xen/efi.c, too. >>>>>> >>>>>> If you wish we can go that way too. Though I thing that we should fix >>>>>> drivers/firmware/efi/reboot.c:efi_shutdown_init() too. Just in case. >>>>> >>>>> Sure, go ahead. I won't object. >>>> >>>> For the Xen on ARM side, the original patch that started this thread >>>> (20170405181417.15985-1-julien.grall@arm.com) is good to go, right? >>>> >>> >>> As I said: the dummy xen_efi_reset_system() should be in >>> drivers/xen/efi.c >> >> OK. Who is working on it? > > Didn't Julien say he would do it? Yes. I looked at bit closer to the problem mention with power off. xen_efi_reset_system cannot be a NOP because there may not be fallback alternatives (see machine_power_off in arch/arm64/kernel/process.c) So I think we would have to translate EFI_RESET* to Xen SHUTDOWN_* and then call HYPERVISOR_sched_op directly. I will send a new version soon. Cheers, -- Julien Grall