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Date: Mon, 25 May 2015 11:30:02 +1000
From: David Gibson <david@gibson.dropbear.id.au>
Message-ID: <20150525013002.GG6255@voom.redhat.com>
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In-Reply-To: <20150513102818.31240.99013.stgit@bahia.huguette.org>
Subject: Re: [Qemu-devel] [PATCH] spapr: ensure we have at least one XICS
	server
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To: Greg Kurz <gkurz@linux.vnet.ibm.com>
Cc: qemu-ppc@nongnu.org, qemu-devel@nongnu.org, bharata@linux.vnet.ibm.com


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On Wed, May 13, 2015 at 12:29:33PM +0200, Greg Kurz wrote:
> XICS needs to know the upper value for cpu_index as it is used to compute
> the number of servers:
>=20
>     smp_cpus * kvmppc_smt_threads() / smp_threads
>=20
> When passing -smp cpus=3D1,threads=3D9 on a POWER8 host, we end up with:
>=20
>     1 * 8 / 9 =3D 0
>=20
> ... which leads to an assertion in both emulated:
>=20
> Number of servers needs to be greater 0
> Aborted (core dumped)
>=20
> ... and in-kernel XICS:
>=20
> xics_kvm_realize: Assertion `icp->nr_servers' failed.
> Aborted (core dumped)
>=20
> With this patch, we are sure that nr_servers > 0. Passing the same bogus
> -smp option then leads to:
>=20
> qemu-system-ppc64: Cannot support more than 8 threads on PPC with KVM
>=20
> ... which is a lot more explicit than the XICS errors.
>=20
> Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>

Looks sensible, thanks.

Applied to spapr-next branch.

--=20
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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