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Re: [Qemu-ppc] [RFC PATCH 09/26] ppc/xive: add an overall memory region


From: David Gibson
Subject: Re: [Qemu-ppc] [RFC PATCH 09/26] ppc/xive: add an overall memory region for the ESBs
Date: Mon, 24 Jul 2017 16:39:05 +1000
User-agent: Mutt/1.8.3 (2017-05-23)

On Mon, Jul 24, 2017 at 04:09:31PM +1000, Benjamin Herrenschmidt wrote:
> On Mon, 2017-07-24 at 14:49 +1000, David Gibson wrote:
> > On Wed, Jul 05, 2017 at 07:13:22PM +0200, Cédric Le Goater wrote:
> > > Each source adds its own ESB mempry region to the overall ESB memory
> > > region of the controller. It will be mapped in the CPU address space
> > > when XIVE is activated.
> > > 
> > > The default mapping address for the ESB memory region is the same one
> > > used on baremetal.
> > > 
> > > Signed-off-by: Cédric Le Goater <address@hidden>
> > > ---
> > >  hw/intc/xive-internal.h |  5 +++++
> > >  hw/intc/xive.c          | 44 +++++++++++++++++++++++++++++++++++++++++++-
> > >  2 files changed, 48 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/hw/intc/xive-internal.h b/hw/intc/xive-internal.h
> > > index 8e755aa88a14..c06be823aad0 100644
> > > --- a/hw/intc/xive-internal.h
> > > +++ b/hw/intc/xive-internal.h
> > > @@ -98,6 +98,7 @@ struct XIVE {
> > >      SysBusDevice parent;
> > >  
> > >      /* Properties */
> > > +    uint32_t     chip_id;
> > 
> > So there is a XIVE object per chip.  How does this work on PAPR?  One
> > logical chip/XIVE, or something more complex?
> 
> One global XIVE for PAPR. For the MMIOs, the way it works is that:
> 
>  - For MMIOs pertaining to a specific interrupt or queue, there's an H-
> call that will return the proper "guest physical" address. For qemu
> with KVM we'll have to probably create a single chunk of qemu address
> space (a single mem region) that contains individual pages mapped with
> MAP_FIXED originating from the different HW bits, we still need to sort
> out how exactly we'll do that in practice.
> 
>  - For the TIMA (the presentation MMIOs), those are always at the same
> physical address for everybody (so for a guest it's a single memory
> region we'll map to that physical address), the HW "knows" which HW
> thread is talking to it (and the hypervisor tells the HW which vcpu is
> running on a given HW thread at a given point in time). That address is
> obtained from the device-tree

Ok.  That leaves "chip_id" as a rather surprising thing to see in an
object which will appear on PAPR.

-- 
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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