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

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Date:   Tue, 18 Apr 2017 11:37:01 -0700 (PDT)
From:   Stefano Stabellini <sstabellini@...nel.org>
To:     Juergen Gross <jgross@...e.com>
cc:     Daniel Kiper <daniel.kiper@...cle.com>,
        Julien Grall <julien.grall@....com>,
        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

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?