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From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Mon, 24 Jul 2017 18:56:29 +1000
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Subject: Re: [Qemu-devel] [RFC PATCH 07/26] ppc/xive: add MMIO handlers to
 the XIVE interrupt source
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To: David Gibson <david@gibson.dropbear.id.au>, =?ISO-8859-1?Q?C=E9dric?= Le Goater <clg@kaod.org>
Cc: Alexander Graf <agraf@suse.de>, qemu-ppc@nongnu.org, qemu-devel@nongnu.org

On Mon, 2017-07-24 at 14:29 +1000, David Gibson wrote:
> > +    case XIVE_ESB_SET_PQ_00:
> > +    case XIVE_ESB_SET_PQ_01:
> > +    case XIVE_ESB_SET_PQ_10:
> > +    case XIVE_ESB_SET_PQ_11:
> > +        ret = xive_pq_get(x, lisn);
> > +        xive_pq_set(x, lisn, (offset >> 8) & 0x3);
> 
> Again I'd prefer xive_pq_set() return the old value itself, for more
> obvious atomicity.

Agreed.  That will also help with StoreEOI (store to 0x400 of the EOI
page) which does an EOI then re-sends an interrupt if the old value was
11 (while the load EOI doesn't resend).

Cheers,
Ben.