ppc/spapr: Initialize max_cpus limit to SPAPR_IRQ_NR_IPIS.
Initialize the machine specific max_cpus limit as per the maximum range
of CPU IPIs available. Keeping between 4096 to 8192 will throw IRQ not
free error due to XIVE/XICS limitation and keeping beyond 8192 will hit
assert in tcg_region_init or spapr_xive_claim_irq.
Logs:
Without patch fix:
[root@host build]# qemu-system-ppc64 -accel tcg -smp 10,maxcpus=4097
qemu-system-ppc64: IRQ 4096 is not free
[root@host build]#
On LPAR:
[root@host build]# qemu-system-ppc64 -accel tcg -smp 10,maxcpus=8193
**
ERROR:../tcg/region.c:774:tcg_region_init: assertion failed:
(region_size >= 2 * page_size)
Bail out! ERROR:../tcg/region.c:774:tcg_region_init: assertion failed:
(region_size >= 2 * page_size)
Aborted (core dumped)
[root@host build]#
On x86:
[root@host build]# qemu-system-ppc64 -accel tcg -smp 10,maxcpus=8193
qemu-system-ppc64: ../hw/intc/spapr_xive.c:596: spapr_xive_claim_irq:
Assertion `lisn < xive->nr_irqs' failed.
Aborted (core dumped)
[root@host build]#
With patch fix:
[root@host build]# qemu-system-ppc64 -accel tcg -smp 10,maxcpus=4097
qemu-system-ppc64: Invalid SMP CPUs 4097. The max CPUs supported by
machine 'pseries-8.2' is 4096
[root@host build]#
Reported-by: Kowshik Jois <kowsjois@linux.ibm.com>
Tested-by: Kowshik Jois <kowsjois@linux.ibm.com>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 0d72d28..0028ce0 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -4639,13 +4639,10 @@
mc->block_default_type = IF_SCSI;
/*
- * Setting max_cpus to INT32_MAX. Both KVM and TCG max_cpus values
- * should be limited by the host capability instead of hardcoded.
- * max_cpus for KVM guests will be checked in kvm_init(), and TCG
- * guests are welcome to have as many CPUs as the host are capable
- * of emulate.
+ * While KVM determines max cpus in kvm_init() using kvm_max_vcpus(),
+ * In TCG the limit is restricted by the range of CPU IPIs available.
*/
- mc->max_cpus = INT32_MAX;
+ mc->max_cpus = SPAPR_IRQ_NR_IPIS;
mc->no_parallel = 1;
mc->default_boot_order = "";
