Re: [Qemu-ppc] [SLOF] [PATCH v4] board-qemu: add private hcall to inform host on "phandle" update

[David Gibson]

On Thu, Sep 14, 2017 at 10:56:49AM -0500, Segher Boessenkool wrote:
> On Thu, Sep 14, 2017 at 11:48:28AM +1000, David Gibson wrote:
> > On Wed, Sep 13, 2017 at 06:21:52PM -0500, Segher Boessenkool wrote:
> > > On Sat, Sep 09, 2017 at 01:38:29PM +1000, David Gibson wrote:
> > > > [Aside: strictly, it's not an FDT piece that goes to the guest OS;
> > > > the guest performs a sequence of calls to traverse the DT fragment.
> > > > qemu uses an fdt fragment as an internal detail, but that's not part
> > > > of the protocol]
> > > 
> > > Ah that is good to hear :-)
> > 
> > It's really not.  Spitting in a chunk of FDT would be a simpler and
> > more efficient method of accomplishing the same thing as the horrid
> > set of PAPR mandated RTAS calls (these are *not* the same as the
> > regular OF calls used at boot time - the boot time OF client interface
> > is long gone).  But then, I guess FDT wasn't a thing when that bit of
> > the PAPR spec was made.
> 
> Ah, I thought you meant client interface.  Yeah, bah :-(
> 
> > > By the time qemu is queried for this information it should already know
> > > the real phandle of the interrupt controller;
> > 
> > Nope.  How would it?  After it fires it off, qemu is no longer in
> > communication with SLOF.
> 
> Qemu emulates the hardware SLOF runs on, there is a gazillion ways it
> can communicate.  You just have to figure out something reasonable.

Well, sure, and the patch which started this thread was a proposal for
one such.

-- 
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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