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

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Message-ID: <e449f220-8db7-d58c-bdbf-47ccd6dd014b@arm.com>
Date:   Thu, 6 Apr 2017 16:39:13 +0100
From:   Julien Grall <julien.grall@....com>
To:     Daniel Kiper <daniel.kiper@...cle.com>,
        Juergen Gross <jgross@...e.com>
Cc:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        xen-devel@...ts.xen.org, sstabellini@...nel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: xen: Implement EFI reset_system callback

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.

Cheers,

-- 
Julien Grall