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Re: [PATCH v2 0/2] spapr: Fix device unplug vs CAS or migration


From: David Gibson
Subject: Re: [PATCH v2 0/2] spapr: Fix device unplug vs CAS or migration
Date: Mon, 17 Feb 2020 11:31:37 +1100

On Fri, Feb 14, 2020 at 04:01:16PM +0100, Greg Kurz wrote:
> While working on getting rid of CAS reboot, I realized that we currently
> don't handle device hot unplug properly in the following situations:
> 
> 1) if the device is unplugged between boot and CAS, SLOF doesn't handle
>    the even, which is a known limitation. The device hence stays around
>    forever (specifically, until some other event is emitted and the guest
>    eventually completes the unplug or a reboot). Until we can teach SLOF
>    to correctly process the full FDT at CAS, we should trigger a CAS reboot,
>    like we already do for hotplug.
> 
> 2) if the guest is migrated after the even was emitted but before the
>    guest could process it, the destination is unaware of the pending
>    unplug operation and doesn't remove the device when the guests
>    releases it. The 'unplug_requested' field of the DRC is actually state
>    that should be migrated.
> 
> Changes since v1:
>    - new spapr_drc_transient() helper that covers pending plug and unplug
>      situations for both CAS and migration
>    - as a mechanical consequence, fix unplug for CAS an migration in the
>      same patch

Applied to ppc-for-5.0, thanks.

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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