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    SubjectRe: [PATCH] arm64: xen: Implement EFI reset_system callback
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    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.


    Juergen

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