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Date:   Sun, 13 Sep 2020 13:07:36 -0400
To:     Anchal Agarwal <>,,,,,,,,,,,,,,,,,,,,,,,,,,
Subject: Re: [PATCH v3 01/11] xen/manage: keep track of the on-going suspend

On 8/21/20 6:25 PM, Anchal Agarwal wrote:
> From: Munehisa Kamata <>  
> Guest hibernation is different from xen suspend/resume/live migration.
> Xen save/restore does not use pm_ops as is needed by guest hibernation.
> Hibernation in guest follows ACPI path and is guest inititated , the
> hibernation image is saved within guest as compared to later modes
> which are xen toolstack assisted and image creation/storage is in
> control of hypervisor/host machine.
> To differentiate between Xen suspend and PM hibernation, keep track
> of the on-going suspend mode by mainly using a new API to keep track of
> Introduce a simple function that keeps track of on-going suspend mode
> so that PM hibernation code can behave differently according to the
> current suspend mode.
> Since Xen suspend doesn't have corresponding PM event, its main logic
> is modfied to acquire pm_mutex.
> Though, accquirng pm_mutex is still right thing to do, we may
> see deadlock if PM hibernation is interrupted by Xen suspend.
> PM hibernation depends on xenwatch thread to process xenbus state
> transactions, but the thread will sleep to wait pm_mutex which is
> already held by PM hibernation context in the scenario. Xen shutdown
> code may need some changes to avoid the issue.
> [Anchal Agarwal: Changelog]:
>  RFC v1->v2: Code refactoring
>  v1->v2:     Remove unused functions for PM SUSPEND/PM hibernation
>  v2->v3:     Added logic to use existing pm_notifier to detect for ARM
> 	     and abort hibernation for ARM guests. Also removed different
> 	     suspend_modes and simplified the code with using existing state
> 	     variables for tracking Xen suspend. The notifier won't get
> 	     registered for pvh dom0 either.
> Signed-off-by: Anchal Agarwal <>
> Signed-off-by: Munehisa Kamata <>

BTW, just to make sure --- Thomas' comments about commit message format
(SoB order, no changelog, etc) apply to all patches, not just #5.


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