[Xen-devel] Re: [linux-pm] [PATCH 0/3] xen: Use PM/Hibernate events for save/restore/chkpt

[Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>]

On Mon, 21 Feb 2011, Ian Campbell wrote:

> On Sun, 2011-02-20 at 07:49 +0000, Pavel Machek wrote:
> > On Sat 2011-02-19 15:12:35, Shriram Rajagopalan wrote:
> > > The current implementation of xen guest save/restore/checkpoint 
> > > functionality
> > > uses PM_SUSPEND and PM_RESUME events. This is not optimal when taking
> > > checkpoints of a virtual machine (where the suspend hypercall returns
> > > non-zero, requiring the devices and xenbus to just pickup from where they 
> > > left
> > > off instead of a complete teardown/reconnect to backend). 
> > > 
> > > The following set of patches modify this implementation to use Hibernate 
> > > style
> > > control flow (freeze/restore for save/restore and freeze/thaw for 
> > > checkpoint,
> > > which is merely a cancelled save akin to failed swsusp() ).
> > > 
> > > These patches are against Ian Campbell's PVHVM tree at
> > > git://xenbits.xen.org/people/ianc/linux-2.6.git for-stefano/pvhvm
> > > 
> > > at commit 8a8d1bc753c4e2dda5f2890292d60c67d6ebb573
> > > kernel version: 2.6.38-rc4
> > 
> > Series looks ok to me...
> 
> Thanks Pavel, may we take that as an Acked-by?
> 
> For my part the Xen side is:
> Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

There's one part of this which could be troublesome.  The new code 
generates FREEZE, THAW, and RESTORE events even in kernels where 
CONFIG_HIBERNATION isn't set.  In such kernels, drivers are not 
obliged to handle these events correctly.

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.

Alan Stern


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