From 2bc2c4a8105f3e3bce457cc6446cf3a13e98a827 Mon Sep 17 00:00:00 2001 From: "Ritesh Harjani (IBM)" Date: Tue, 6 Oct 2026 15:58:37 +0530 Subject: [PATCH] KVM: selftests: Skip the max vCPU ID test when KVM_CAP_PPC_SMT is set kvm_create_max_vcpus creates vCPUs from 0..MAX_VCPUS-1, then again with ids at the top of KVM_CAP_MAX_VCPU_ID. On PowerPC the vCPU id is not a flat index: it encodes SMT thread plus core. So on powerpc maximum permitted vCPU ID depends on the VM's SMT mode and the maximum reported by KVM_CAP_MAX_VCPU_ID exceeds a simple non-SMT VM's limit. So, skip that second loop when KVM_CAP_PPC_SMT is non-zero. The cap is 0 on other arches, so they still run it. The 0..MAX_VCPUS pass is unchanged. Suggested-by: Sean Christopherson Tested-by: Anushree Mathur Signed-off-by: Ritesh Harjani (IBM) Reviewed-by: Gautam Menghani Tested-by: Gautam Menghani Acked-by: Madhavan Srinivasan Link: https://patch.msgid.link/bbfbaa9fb2eca8c92f59dc980546c2587dcfc130.1791280439.git.ritesh.list@gmail.com Signed-off-by: Sean Christopherson --- tools/testing/selftests/kvm/kvm_create_max_vcpus.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/kvm/kvm_create_max_vcpus.c b/tools/testing/selftests/kvm/kvm_create_max_vcpus.c index c5310736ed06..1b95027d41ba 100644 --- a/tools/testing/selftests/kvm/kvm_create_max_vcpus.c +++ b/tools/testing/selftests/kvm/kvm_create_max_vcpus.c @@ -58,7 +58,13 @@ int main(int argc, char *argv[]) test_vcpu_creation(0, kvm_max_vcpus); - if (kvm_max_vcpu_id > kvm_max_vcpus) + /* + * Skip the vCPU ID test when running on PowerPC with SMT support, in + * which case system topology is encoded into the vCPU ID and so a VM + * can't use the full advertised vCPU ID range without crafting a valid + * platform specific topology. + */ + if (kvm_max_vcpu_id > kvm_max_vcpus && !kvm_check_cap(KVM_CAP_PPC_SMT)) test_vcpu_creation( kvm_max_vcpu_id - kvm_max_vcpus, kvm_max_vcpus);