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KVM: selftests: Skip the max vCPU ID test when KVM_CAP_PPC_SMT is set

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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 <seanjc@google.com>
Tested-by: Anushree Mathur <anushree.mathur@linux.ibm.com>
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Reviewed-by: Gautam Menghani <gautam@linux.ibm.com>
Tested-by: Gautam Menghani <gautam@linux.ibm.com>
Acked-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/bbfbaa9fb2eca8c92f59dc980546c2587dcfc130.1791280439.git.ritesh.list@gmail.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Ritesh Harjani (IBM) 2026-10-06 15:58:37 +05:30 committed by Sean Christopherson
parent f51639c0ee
commit 2bc2c4a810
1 changed files with 7 additions and 1 deletions
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8
tools/testing/selftests/kvm/kvm_create_max_vcpus.c
View File

@ -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);