Re: [PATCH 0/3] xen: Use PM/Hibernate events for save/restore/chkpt

From: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
To: Ian Campbell <Ian.Campbell@eu.citrix.com>
Cc: "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
	Stefano Stabellini <Stefano.Stabellini@eu.citrix.com>,
	Shriram Rajagopalan <rshriram@cs.ubc.ca>,
	"linux-pm@lists.linux-foundation.org"
	<linux-pm@lists.linux-foundation.org>
Subject: Re: [PATCH 0/3] xen: Use PM/Hibernate events for save/restore/chkpt
Date: Fri, 25 Feb 2011 16:23:31 +0000	[thread overview]
Message-ID: <alpine.DEB.2.00.1102251622400.19277__3523.52657723731$1298651337$gmane$org@kaball-desktop> (raw)
In-Reply-To: <1298650792.5034.551.camel@zakaz.uk.xensource.com>

On Fri, 25 Feb 2011, Ian Campbell wrote:
> On Fri, 2011-02-25 at 16:17 +0000, Stefano Stabellini wrote:
> > On Mon, 21 Feb 2011, Rafael J. Wysocki wrote:
> > > > For a PV guest only the Xen PV drivers really matter.
> > > > 
> > > > But for a PVHVM guest you are right since there are the emulated "PC"
> > > > devices though which could be problematic. There's nothing especially
> > > > thrilling in that set of devices although I don't think that invalidates
> > > > your point.
> > 
> > This is a genuine concern because it currently breaks save/restore for
> > all PV on HVM guests (dummy_hcd being the offending driver).
> 
> Only if !CONFIG_HIBERNATION, right?

Yes

> > > > > Shouldn't the CONFIG_XEN_SAVE_RESTORE option select CONFIG_HIBERNATION?
> > > > > In which case the #ifdef lines in pm_op() wouldn't need to be changed.
> > > > 
> > > > I think selecting user-visible symbols is generally frowned upon.
> > > > 
> > > > But apart from that I was concerned that tying the Xen functionality
> > > > into the hibernation option was a bit odd/artificial. Perhaps it's the
> > > > only solution though.
> > > 
> > > I'd very much prefer it if the patchset didn't touch drivers/base/power/main.c.
> > > 
> > > However, if you want to select CONFIG_HIBERNATION from CONFIG_XEN_SAVE_RESTORE,
> > > you should make sure that CONFIG_HIBERNATION is really selectable (ie.
> > > CONFIG_SWAP is set and CONFIG_ARCH_HIBERNATION_POSSIBLE is set).
> > 
> > I think we should follow this suggestion.
> 
> See the thread "[PATCH] xen: fix XEN_SAVE_RESTORE Kconfig dependencies"
> from Shriram <1298446066-11754-1-git-send-email-rshriram@cs.ubc.ca>

Thanks, I am a bit behind schedule with my unread emails...