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

[Segher Boessenkool]

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.


Segher