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Re: [Qemu-devel] [PATCH 14/25] spapr: push the XIVE EQ data in OS event
From: |
David Gibson |
Subject: |
Re: [Qemu-devel] [PATCH 14/25] spapr: push the XIVE EQ data in OS event queue |
Date: |
Mon, 4 Dec 2017 12:20:29 +1100 |
User-agent: |
Mutt/1.9.1 (2017-09-22) |
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
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