Re: [Qemu-devel] [PATCH 14/25] spapr: push the XIVE EQ data in OS event queue

[David Gibson]

On Sat, Dec 02, 2017 at 08:46:19AM -0600, Benjamin Herrenschmidt wrote:
> On Sat, 2017-12-02 at 08:45 -0600, Benjamin Herrenschmidt wrote:
> > On Fri, 2017-12-01 at 15:10 +1100, David Gibson wrote:
> > > 
> > > Hm, ok.  Guest endian (or at least, not definitively host-endian) data
> > > in a plain uint32_t makes me uncomfortable.  Could we use char data[4]
> > > instead, to make it clear it's a byte-ordered buffer, rather than a
> > > number as far as the XIVE is concerned.
> > > 
> > > Hm.. except that doesn't quite work, because the hardware must define
> > > which end that generation bit ends up in...
> > 
> > It also needs to be written atomically. Just say it's big endian.
> 
> Also the guest reads it using be32_to_cpup...

Ok.  Definitely should be treated as BE and read/written with the be32
DMA helper functions.

-- 
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

signature.asc
Description: PGP signature