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Re: [PATCH 0/3] spapr: Fix device unplug vs CAS or migration
From: |
David Gibson |
Subject: |
Re: [PATCH 0/3] spapr: Fix device unplug vs CAS or migration |
Date: |
Fri, 14 Feb 2020 13:29:25 +1100 |
On Thu, Feb 13, 2020 at 04:10:55PM +0100, Greg Kurz wrote:
> Ping ?
>
> This series fixes actual bugs. Also, I have another patch on top of
> that to cold plug (or remove) devices pending hot plug (or unplug)
> before CAS, hence removing the need for CAS reboot in these cases.
> This requires SLOF to correctly parse the FDT it gets at CAS. Patches
> have been sent for that too:
>
> https://git.qemu.org/?p=SLOF.git;a=commitdiff;h=689ff6f6554d94fdab854bf4fc4ec85e2675e43d
> https://git.qemu.org/?p=SLOF.git;a=commitdiff;h=a093be1ebe7a48321646601d94be6cf735c81e12
> https://patchwork.ozlabs.org/patch/1235817/
Yeah, sorry, I've been having a bit of trouble getting my head around
the cases here. I've sent a comment now.
>
> On Mon, 03 Feb 2020 23:36:04 +0100
> Greg Kurz <address@hidden> 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.
> >
>
--
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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