linux-kernel - Re: [Xen-devel] [PATCH v3] xen: Suspend ticks on all CPUs during suspend

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Message-ID: <5541027A.90206@citrix.com>
Date:	Wed, 29 Apr 2015 17:10:34 +0100
From:	David Vrabel <david.vrabel@...rix.com>
To:	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	<david.vrabel@...rix.com>, <konrad.wilk@...cle.com>
CC:	<xen-devel@...ts.xenproject.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [Xen-devel] [PATCH v3] xen: Suspend ticks on all CPUs during
 suspend

On 28/04/15 23:46, Boris Ostrovsky wrote:
> Commit 77e32c89a711 ("clockevents: Manage device's state separately for
> the core") decouples clockevent device's modes from states. With this
> change when a Xen guest tries to resume, it won't be calling its
> set_mode op which needs to be done on each VCPU in order to make the
> hypervisor aware that we are in oneshot mode.
> 
> This happens because clockevents_tick_resume() (which is an intermediate
> step of resuming ticks on a processor) doesn't call clockevents_set_state()
> anymore and because during suspend clockevent devices on all VCPUs (except
> for the one doing the suspend) are left in ONESHOT state. As result, during
> resume the clockevents state machine will assume that device is already
> where it should be and doesn't need to be updated.
> 
> To avoid this problem we should suspend ticks on all VCPUs during
> suspend.

Applied to for-linus-4.1b, thanks.

David
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