linux-kernel - Re: [PATCH v4 0/5] Xen/ACPI: support sleep state entering on hardware reduced systems

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Date:	Sat, 27 Jul 2013 15:33:31 +0000
From:	Ben Guthro <Ben.Guthro@...rix.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
CC:	Ben Guthro <Ben.Guthro@...rix.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Jan Beulich <jbeulich@...e.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"xen-devel@...ts.xen.org" <xen-devel@...ts.xen.org>,
	Richard L Maliszewski <richard.l.maliszewski@...el.com>,
	Gang Wei <gang.wei@...el.com>,
	Shane Wang <shane.wang@...el.com>,
	Bob Moore <robert.moore@...el.com>,
	"tboot-devel@...ts.sourceforge.net" 
	<tboot-devel@...ts.sourceforge.net>
Subject: Re: [PATCH v4 0/5] Xen/ACPI: support sleep state entering on
 hardware reduced systems



On Jul 27, 2013, at 9:51 AM, "Rafael J. Wysocki" <rjw@...k.pl> wrote:

> On Thursday, June 27, 2013 11:01:58 AM Ben Guthro wrote:
>> In version 3.4 acpi_os_prepare_sleep() got introduced in parallel with
>> reduced hardware sleep support, and the two changes didn't get
>> synchronized: The new code doesn't call the hook function (if so
>> requested). Fix this, requiring a boolean parameter to be added to the
>> hook function to distinguish "extended" from "legacy" sleep.
>> 
>> This requires adjusting TXT, but the adjustments only go as far as
>> failing the extended mode call (since, looking at the TXT interface,
>> there doesn't even appear to be precautions to deal with that
>> alternative interface).
>> 
>> The hypervisor change underlying this is commit 62d1a69 ("ACPI: support
>> v5 (reduced HW) sleep interface") on the master branch of
>> git://xenbits.xen.org/xen.git.
>> 
>> Signed-off-by: Ben Guthro <benjamin.guthro@...rix.com>
>> Signed-off-by: Jan Beulich <jbeulich@...e.com>
>> Cc: Richard L Maliszewski <richard.l.maliszewski@...el.com>
>> Cc: Gang Wei <gang.wei@...el.com>
>> Cc: Shane Wang <shane.wang@...el.com>
>> Cc: Bob Moore <robert.moore@...el.com>
>> Cc: Rafaell J. Wysocki <rjw@...k.pl>
>> Cc: linux-acpi@...r.kernel.org
>> Cc: tboot-devel@...ts.sourceforge.net 
>> 
>> v2: Extend description to include reference to hypervisor side change
>> v3: Split into multiple patches, separating subsystems
>>    Remove bool parameters, in favor of u8
>> v4: Remove linux/acpi.h dependencies
>>    Further patch split to break out acpica from OSL
>>    More bool vs u8 fixes
>> 
>> Ben Guthro (5):
>>  acpi: Remove need to include linux/acpi.h in common acpica code
>>  acpi: Call acpi_os_prepare_sleep hook in reduced hardware sleep path
>>  acpi: Adjust linux acpi OS functions to new extended parameter
>>  x86/tboot: Fail extended mode reduced hardware sleep
>>  xen/acpi: notify xen when reduced hardware sleep is available
> 
> The ongoing discussion means to me that the ACPICA maintainers don't want
> acpi_os_prepare_sleep() and quite frankly I understand them, because ACPICA
> is about implementing the spec and not about things beyond it.
> 
> This means that patch [1/5] goes away.
> 
> That said, at the same time we need to address the problem at hand, which
> is to make Xen work with the reduced HW sleep.
> 
> For that, I don't honestly think that modifying acpi_os_prepare_sleep() the
> way the patchset is doing it is appropriate and the change of the meaning of
> the arguments is simply disgusting.
> 
> To me, it would be much cleaner to add acpi_os_prepare_extended_sleep()
> specifically to be called by acpi_hw_extended_sleep() and make tboot and Xen
> use that.
> 
> This way or another, we'll need to live with one more divergence between the
> upstream ACPICA and the Linux ACPICA code because of that, but that'd be just
> a few added lines in acpi_hw_extended_sleep(), so I suppose it wouldn't be
> such a big deal.
> 

Ok, thank you for the review, and being open to addressing the problem at hand, without a full architecture rework (not to say that that discussion is not also needed)

I will try to make some time next week to rework the patch set to address these concerns, and submit a new series. 

Thanks
Ben



> Thanks,
> Rafael
> 
> 
> -- 
> I speak only for myself.
> Rafael J. Wysocki, Intel Open Source Technology Center.
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