Re: [Xen-devel] [PATCH] Use freeze/thaw/restore PM events for Guest suspend/resume/checkpoint

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2011-02-14 at 16:21 +0000, Shriram Rajagopalan wrote:
> Use PM_FREEZE, PM_THAW and PM_RESTORE power events for
> suspend/resume functionality, instead of PM_SUSPEND and
> PM_RESUME. Use of these pm events also fixes the Xen Guest
> hangup when taking checkpoints. When a suspend event is cancelled
> (i.e. while taking checkpoints once/continuously), we use PM_THAW
> instead of PM_RESUME. PM_RESTORE is used when suspend is not
> cancelled. See Documentation/power/devices.txt and linux/pm.h
> for more info about freeze, thaw and restore. The sequence of
> pm events in a suspend-resume scenario is shown below.
> 
>       dpm_suspend_start(PMSG_FREEZE);
> 
>               dpm_suspend_noirq(PMSG_FREEZE);
> 
>                        sysdev_suspend(PMSG_FREEZE);
>                        cancelled = suspend_hypercall()
>                        sysdev_resume();
> 
>                dpm_resume_noirq(cancelled ? PMSG_THAW : PMSG_RESTORE);
> 
>        dpm_resume_end(cancelled ? PMSG_THAW : PMSG_RESTORE);

Thanks.

Which tree/branch is this against?

Can you please at least do the dev_pm_ops as a separate patch to allow
bisectability etc. (generally each patch should be a single logical
change so if the remaineder can be sensibly split too it is worth doing
so).

Did you test regular save/restore as well as cancelled migrations? What
about PVHMV guests?

> +static struct dev_pm_ops xenbus_pm_ops = {
> +     .suspend = xenbus_dev_suspend,
> +     .resume  = xenbus_dev_resume,
> +     .freeze  = xenbus_dev_suspend,
> +     .thaw    = xenbus_dev_cancel,
> +     .restore = xenbus_dev_resume,
> +};

Perhaps xenbus_dev_thaw?

Are suspend/freeze and resume/restore really the same?

Once we've transitioned to the PMSG_FREEZE way of doing things do we
still need to keep the other hooks around? If not then the other ones
could be renamed as well?

On Mon, 2011-02-14 at 16:24 +0000, Shriram Rajagopalan wrote:
> parts of this patch were based on Kazuhiro Suzuki's initial patch to
> fix the same issue. Refer to
> http://lists.xensource.com/archives/html/xen-devel/2011-02/msg00371.html
> for further details.

It's worth mentioning this in the commit message, also please CC
Kazuhiro since he has been working on this too, has a repro scenario
etc.

Ian.


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