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

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Message-ID: <alpine.DEB.2.10.1704181145420.31486@sstabellini-ThinkPad-X260>
Date:   Tue, 18 Apr 2017 11:46:27 -0700 (PDT)
From:   Stefano Stabellini <sstabellini@...nel.org>
To:     Juergen Gross <jgross@...e.com>
cc:     Stefano Stabellini <sstabellini@...nel.org>,
        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 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@....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?