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[Qemu-ppc] [PATCH 01/22] spapr: ensure we have at least one XICS server

From: David Gibson
Subject: [Qemu-ppc] [PATCH 01/22] spapr: ensure we have at least one XICS server
Date: Wed, 24 Jun 2015 16:30:15 +1000

From: Greg Kurz <address@hidden>

XICS needs to know the upper value for cpu_index as it is used to compute
the number of servers:

    smp_cpus * kvmppc_smt_threads() / smp_threads

When passing -smp cpus=1,threads=9 on a POWER8 host, we end up with:

    1 * 8 / 9 = 0

... which leads to an assertion in both emulated:

Number of servers needs to be greater 0
Aborted (core dumped)

... and in-kernel XICS:

xics_kvm_realize: Assertion `icp->nr_servers' failed.
Aborted (core dumped)

With this patch, we are sure that nr_servers > 0. Passing the same bogus
-smp option then leads to:

qemu-system-ppc64: Cannot support more than 8 threads on PPC with KVM

... which is a lot more explicit than the XICS errors.

Signed-off-by: Greg Kurz <address@hidden>
Signed-off-by: David Gibson <address@hidden>
 hw/ppc/spapr.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index f174e5a..10ca866 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1467,7 +1467,8 @@ static void ppc_spapr_init(MachineState *machine)
     /* Set up Interrupt Controller before we create the VCPUs */
     spapr->icp = xics_system_init(machine,
-                                  smp_cpus * kvmppc_smt_threads() / 
+                                  DIV_ROUND_UP(smp_cpus * kvmppc_smt_threads(),
+                                               smp_threads),
     /* init CPUs */

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