linux-kernel - Re: [PATCH] arm64: xen: Implement EFI reset

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Message-ID: <fcc5ac4b-ed82-b5dd-a848-9ac9a3572853@suse.com>
Date:   Tue, 18 Apr 2017 20:43:03 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Stefano Stabellini <sstabellini@...nel.org>
Cc:     Daniel Kiper <daniel.kiper@...cle.com>,
        Julien Grall <julien.grall@....com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        xen-devel@...ts.xen.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: xen: Implement EFI reset_system callback

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@....com) is good to go, right?
> 

As I said: the dummy xen_efi_reset_system() should be in
drivers/xen/efi.c


Juergen