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

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Message-ID: <20170406164309.GM4372@olila.local.net-space.pl>
Date:   Thu, 6 Apr 2017 18:43:09 +0200
From:   Daniel Kiper <daniel.kiper@...cle.com>
To:     Juergen Gross <jgross@...e.com>
Cc:     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, 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.

Daniel