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

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Date:	Sun, 28 Jul 2013 01:31:52 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Ben Guthro <Ben.Guthro@...rix.com>
Cc:	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 Saturday, July 27, 2013 03:33:31 PM Ben Guthro wrote:
> 
> 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,

No problem, although I'm not exactly happy with it.

> without a full architecture rework (not to say that that discussion is not
> also needed)

Sure, it is 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!

Rafael

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