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 <[email protected]>
---
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 35dca77..92916df 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1475,7 +1475,8 @@ 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() /
smp_threads,
+ DIV_ROUND_UP(smp_cpus * kvmppc_smt_threads(),
+ smp_threads),
XICS_IRQS);
/* init CPUs */
