qemu-devel
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-devel] [RFC PATCH 08/26] ppc/xive: add flags to the XIVE inter


From: David Gibson
Subject: Re: [Qemu-devel] [RFC PATCH 08/26] ppc/xive: add flags to the XIVE interrupt source
Date: Tue, 25 Jul 2017 14:19:23 +1000
User-agent: Mutt/1.8.3 (2017-05-23)

On Mon, Jul 24, 2017 at 01:47:28PM +0200, Cédric Le Goater wrote:
> On 07/24/2017 01:07 PM, Benjamin Herrenschmidt wrote:
> > On Mon, 2017-07-24 at 19:50 +1000, David Gibson wrote:
> >> On Mon, Jul 24, 2017 at 05:00:57PM +1000, Benjamin Herrenschmidt wrote:
> >>> On Mon, 2017-07-24 at 14:36 +1000, David Gibson wrote:
> >>>> On Wed, Jul 05, 2017 at 07:13:21PM +0200, Cédric Le Goater wrote:
> >>>>> These flags define some characteristics of the source :
> >>>>>
> >>>>>  - XIVE_SRC_H_INT_ESB  the Event State Buffer are controlled with a
> >>>>>                        specific hcall H_INT_ESB
> >>>>
> >>>> What's the other option?
> >>>
> >>> Direct MMIO access. Normally all interrupts use normal MMIOs,
> >>> each interrupts has an associated MMIO page with special MMIOs
> >>> to control the source state (PQ bits). This is something I added
> >>> to the PAPR spec (and the OPAL <-> Linux interface) to allow firmware
> >>> to work around broken HW (which happens on some P9 versions).
> >>
> >> Ok.. and that's something that can be decided at runtime?
> > 
> > Well, at this point I think nothing will set that flag.... It's there
> > for workaround around HW bugs on some chips. At least in full emu it
> > shouldn't happen unless we try to emulate those bugs. Hopefully direct
> > MMIO will just work.
> 
> Nevertheless I have added support for the hcall in Linux and QEMU.
> To use, I think we could create a specific source.

So, IIUC, it's host constraints that would make this one way or the
other.  So what happens when a guest migrates from a host which has it
one way to one which has it the other way?

-- 
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

Attachment: signature.asc
Description: PGP signature


reply via email to

[Prev in Thread] Current Thread [Next in Thread]