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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 14:18:41 +1000
User-agent: Mutt/1.8.3 (2017-05-23)

On Mon, Jul 24, 2017 at 09:07:19PM +1000, 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.

Hm.  That doesn't seem like a good match for a per-irq state
structure.

-- 
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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