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

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Message-ID: <90916004-b553-927b-fc8e-2758f8ba04a3@oracle.com>
Date:   Thu, 6 Apr 2017 10:37:11 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Julien Grall <julien.grall@....com>,
        Daniel Kiper <daniel.kiper@...cle.com>
Cc:     Juergen Gross <jgross@...e.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

On 04/06/2017 10:32 AM, Julien Grall wrote:
> Hi Daniel,
>
> On 06/04/17 15:27, 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.
>
> This thread already a fix for ARM64. So do I need to resend a patch
> with x86 fixed or not?

Yes please. Daniel is correct that we are safe with xen_restart().
However, we are not safe when machine_ops.power_off is called.

Thanks.
-boris