* Re: [PATCH] arm64: xen: Implement EFI reset_system callback [not found] ` <e449f220-8db7-d58c-bdbf-47ccd6dd014b-5wv7dgnIgG8@public.gmane.org> @ 2017-04-06 15:55 ` Mark Rutland 2017-04-18 13:46 ` Matt Fleming 0 siblings, 1 reply; 6+ messages in thread From: Mark Rutland @ 2017-04-06 15:55 UTC (permalink / raw) To: Julien Grall Cc: Daniel Kiper, Juergen Gross, Boris Ostrovsky, sstabellini-DgEjT+Ai2ygdnm+yROfE0A, linux-kernel-u79uwXL29TY76Z2rM5mHXA, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r, xen-devel-GuqFBffKawuEi8DpZVb4nw, Matt Fleming, Ard Biesheuvel, linux-efi-u79uwXL29TY76Z2rM5mHXA [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. ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] arm64: xen: Implement EFI reset_system callback 2017-04-06 15:55 ` [PATCH] arm64: xen: Implement EFI reset_system callback Mark Rutland @ 2017-04-18 13:46 ` Matt Fleming [not found] ` <20170418134650.GL24360-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org> 0 siblings, 1 reply; 6+ messages in thread From: Matt Fleming @ 2017-04-18 13:46 UTC (permalink / raw) To: Mark Rutland Cc: Julien Grall, Daniel Kiper, Juergen Gross, Boris Ostrovsky, sstabellini-DgEjT+Ai2ygdnm+yROfE0A, linux-kernel-u79uwXL29TY76Z2rM5mHXA, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r, xen-devel-GuqFBffKawuEi8DpZVb4nw, Ard Biesheuvel, linux-efi-u79uwXL29TY76Z2rM5mHXA 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. ^ permalink raw reply [flat|nested] 6+ messages in thread
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* Re: [PATCH] arm64: xen: Implement EFI reset_system callback [not found] ` <20170418134650.GL24360-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org> @ 2017-04-19 19:29 ` Daniel Kiper [not found] ` <20170419192906.GO16658-fJNZiO034lp9pOct4yEdx/3oZC3j2Omk@public.gmane.org> 0 siblings, 1 reply; 6+ messages in thread From: Daniel Kiper @ 2017-04-19 19:29 UTC (permalink / raw) To: Matt Fleming Cc: Mark Rutland, Julien Grall, Juergen Gross, Boris Ostrovsky, sstabellini-DgEjT+Ai2ygdnm+yROfE0A, linux-kernel-u79uwXL29TY76Z2rM5mHXA, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r, xen-devel-GuqFBffKawuEi8DpZVb4nw, Ard Biesheuvel, linux-efi-u79uwXL29TY76Z2rM5mHXA 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 ^ permalink raw reply [flat|nested] 6+ messages in thread
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* Re: [PATCH] arm64: xen: Implement EFI reset_system callback [not found] ` <20170419192906.GO16658-fJNZiO034lp9pOct4yEdx/3oZC3j2Omk@public.gmane.org> @ 2017-04-19 19:37 ` Matt Fleming 2017-04-19 19:43 ` Daniel Kiper 0 siblings, 1 reply; 6+ messages in thread From: Matt Fleming @ 2017-04-19 19:37 UTC (permalink / raw) To: Daniel Kiper Cc: Mark Rutland, Julien Grall, Juergen Gross, Boris Ostrovsky, sstabellini-DgEjT+Ai2ygdnm+yROfE0A, linux-kernel-u79uwXL29TY76Z2rM5mHXA, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r, xen-devel-GuqFBffKawuEi8DpZVb4nw, Ard Biesheuvel, linux-efi-u79uwXL29TY76Z2rM5mHXA 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(). ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] arm64: xen: Implement EFI reset_system callback 2017-04-19 19:37 ` Matt Fleming @ 2017-04-19 19:43 ` Daniel Kiper 0 siblings, 0 replies; 6+ messages in thread From: Daniel Kiper @ 2017-04-19 19:43 UTC (permalink / raw) To: Matt Fleming Cc: Mark Rutland, Juergen Gross, sstabellini, Ard Biesheuvel, linux-kernel, xen-devel, Julien Grall, linux-efi, Boris Ostrovsky, linux-arm-kernel 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 ^ permalink raw reply [flat|nested] 6+ messages in thread
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* Re: [PATCH] arm64: xen: Implement EFI reset_system callback [not found] ` <b9238471-6957-8720-9c98-37a5a32776d2-IBi9RG/b67k@public.gmane.org> @ 2017-04-20 18:09 ` Julien Grall 0 siblings, 0 replies; 6+ messages in thread From: Julien Grall @ 2017-04-20 18:09 UTC (permalink / raw) To: Juergen Gross, Stefano Stabellini Cc: Daniel Kiper, Boris Ostrovsky, xen-devel-GuqFBffKawuEi8DpZVb4nw, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Mark Rutland, ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A, linux-efi-u79uwXL29TY76Z2rM5mHXA, matt-mF/unelCI9GS6iBeEJttW/XRex20P6io 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-5wv7dgnIgG8@public.gmane.org) 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, -- Julien Grall ^ permalink raw reply [flat|nested] 6+ messages in thread
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2017-04-06 15:55 ` [PATCH] arm64: xen: Implement EFI reset_system callback Mark Rutland
2017-04-18 13:46 ` Matt Fleming
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2017-04-19 19:29 ` Daniel Kiper
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2017-04-19 19:37 ` Matt Fleming
2017-04-19 19:43 ` Daniel Kiper
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2017-04-20 18:09 ` Julien Grall
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