arm64: xen: Implement EFI reset_system callback
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Message ID 20170406152040.GH4372@olila.local.net-space.pl
State New, archived
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Commit Message

Daniel Kiper April 6, 2017, 3:20 p.m. UTC
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:



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.

Daniel

Comments

Julien Grall April 6, 2017, 3:39 p.m. UTC | #1
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.

Cheers,
Mark Rutland April 6, 2017, 3:55 p.m. UTC | #2
[Adding the EFI maintainers]

Tl;DR: Xen's EFI wrappery doesn't implement reset_system, so when
invoked on arm64 we get a NULL dereference.

On Thu, Apr 06, 2017 at 04:39:13PM +0100, Julien Grall wrote:
> 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).

Please, let's keep the Xen knowledge constrained to the Xen EFI wrapper,
rather than spreading it further.

IMO, given reset_system is a *mandatory* function, the Xen wrapper
should provide an implementation.

I don't see why you can't implement a wrapper that calls the usual Xen
poweroff/reset functions.

Thanks,
Mark.
Daniel Kiper April 6, 2017, 4:06 p.m. UTC | #3
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?

Daniel
Jürgen Groß April 6, 2017, 4:22 p.m. UTC | #4
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
Daniel Kiper April 6, 2017, 4:43 p.m. UTC | #5
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
Jürgen Groß April 6, 2017, 5:39 p.m. UTC | #6
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.


Juergen
Matt Fleming April 18, 2017, 1:46 p.m. UTC | #7
On Thu, 06 Apr, at 04:55:11PM, Mark Rutland wrote:
> 
> Please, let's keep the Xen knowledge constrained to the Xen EFI wrapper,
> rather than spreading it further.
> 
> IMO, given reset_system is a *mandatory* function, the Xen wrapper
> should provide an implementation.
> 
> I don't see why you can't implement a wrapper that calls the usual Xen
> poweroff/reset functions.

I realise I'm making a sweeping generalisation, but adding
EFI_PARAVIRT is almost always the wrong thing to do.

I'd much prefer to see Mark's idea implemented.
Stefano Stabellini April 18, 2017, 6:37 p.m. UTC | #8
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@arm.com) is good to go, right?
Jürgen Groß April 18, 2017, 6:43 p.m. UTC | #9
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@arm.com) is good to go, right?
> 

As I said: the dummy xen_efi_reset_system() should be in
drivers/xen/efi.c


Juergen
Stefano Stabellini April 18, 2017, 6:46 p.m. UTC | #10
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@arm.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?
Jürgen Groß April 18, 2017, 6:51 p.m. UTC | #11
On 18/04/17 20:46, Stefano Stabellini wrote:
> 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@arm.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?

Didn't Julien say he would do it?


Juergen
Daniel Kiper April 19, 2017, 7:29 p.m. UTC | #12
On Tue, Apr 18, 2017 at 02:46:50PM +0100, Matt Fleming wrote:
> On Thu, 06 Apr, at 04:55:11PM, Mark Rutland wrote:
> >
> > Please, let's keep the Xen knowledge constrained to the Xen EFI wrapper,
> > rather than spreading it further.
> >
> > IMO, given reset_system is a *mandatory* function, the Xen wrapper
> > should provide an implementation.
> >
> > I don't see why you can't implement a wrapper that calls the usual Xen
> > poweroff/reset functions.
>
> I realise I'm making a sweeping generalisation, but adding
> EFI_PARAVIRT is almost always the wrong thing to do.

Why?

> I'd much prefer to see Mark's idea implemented.

If you wish I do not object.

Daniel
Matt Fleming April 19, 2017, 7:37 p.m. UTC | #13
On Wed, 19 Apr, at 09:29:06PM, Daniel Kiper wrote:
> On Tue, Apr 18, 2017 at 02:46:50PM +0100, Matt Fleming wrote:
> > On Thu, 06 Apr, at 04:55:11PM, Mark Rutland wrote:
> > >
> > > Please, let's keep the Xen knowledge constrained to the Xen EFI wrapper,
> > > rather than spreading it further.
> > >
> > > IMO, given reset_system is a *mandatory* function, the Xen wrapper
> > > should provide an implementation.
> > >
> > > I don't see why you can't implement a wrapper that calls the usual Xen
> > > poweroff/reset functions.
> >
> > I realise I'm making a sweeping generalisation, but adding
> > EFI_PARAVIRT is almost always the wrong thing to do.
> 
> Why?
 
Because it makes paravirt a special case, and there's usually very
little reason to make it special in the EFI code. Special-casing means
more branches, more code paths, a bigger testing matrix and more
complex code. 

EFI_PARAVIRT does have its uses, like for those scenarios where we
don't have a table of function pointers that can be overidden for
paravirt.

But we do have such a table for ->reset_system().
Daniel Kiper April 19, 2017, 7:43 p.m. UTC | #14
On Wed, Apr 19, 2017 at 08:37:38PM +0100, Matt Fleming wrote:
> On Wed, 19 Apr, at 09:29:06PM, Daniel Kiper wrote:
> > On Tue, Apr 18, 2017 at 02:46:50PM +0100, Matt Fleming wrote:
> > > On Thu, 06 Apr, at 04:55:11PM, Mark Rutland wrote:
> > > >
> > > > Please, let's keep the Xen knowledge constrained to the Xen EFI wrapper,
> > > > rather than spreading it further.
> > > >
> > > > IMO, given reset_system is a *mandatory* function, the Xen wrapper
> > > > should provide an implementation.
> > > >
> > > > I don't see why you can't implement a wrapper that calls the usual Xen
> > > > poweroff/reset functions.
> > >
> > > I realise I'm making a sweeping generalisation, but adding
> > > EFI_PARAVIRT is almost always the wrong thing to do.
> >
> > Why?
>
> Because it makes paravirt a special case, and there's usually very
> little reason to make it special in the EFI code. Special-casing means
> more branches, more code paths, a bigger testing matrix and more
> complex code.
>
> EFI_PARAVIRT does have its uses, like for those scenarios where we
> don't have a table of function pointers that can be overidden for
> paravirt.
>
> But we do have such a table for ->reset_system().

This is more or less what I expected. Thanks a lot for explanation.

Daniel
Julien Grall April 20, 2017, 6:09 p.m. UTC | #15
Hi,

On 18/04/17 19:51, Juergen Gross wrote:
> On 18/04/17 20:46, Stefano Stabellini wrote:
>> 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@arm.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?
>
> Didn't Julien say he would do it?

Yes. I looked at bit closer to the problem mention with power off. 
xen_efi_reset_system cannot be a NOP because there may not be fallback 
alternatives (see machine_power_off in arch/arm64/kernel/process.c)

So I think we would have to translate EFI_RESET* to Xen SHUTDOWN_* and 
then call HYPERVISOR_sched_op directly.

I will send a new version soon.

Cheers,

Patch
diff mbox

--- 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())