Re: [PATCH v3 RESEND 05/10] KVM: selftests: Print the vcpu_id when KVM_CREATE_VCPU ioctl fails
From: Sean Christopherson <seanjc@google.com>
Date: 2026-06-10 12:59:32
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On Wed, Jun 10, 2026, Ritesh Harjani (IBM) wrote:
quoted hunk ↗ jump to hunk
Print the vcpu_id and errno when the KVM_CREATE_VCPU ioctl fails, for debug purposes. This helped in debugging an issue with KVM on PowerVM, where KVM_CREATE_VCPU only supports max 2048 vcpus, because the PAPR_HCALL H_GUEST_CREATE_VCPU ("Documentation/arch/powerpc/kvm-nested.rst") supports only up to 0-2047 vcpu_id. However KVM_CAP_MAX_VCPUS capability extension always reports max_vcpus as NR_CPUS of the host. Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com> --- tools/testing/selftests/kvm/lib/kvm_util.c | 7 +++++++ 1 file changed, 7 insertions(+)diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c index e00a25f59416..6319e2037882 100644 --- a/tools/testing/selftests/kvm/lib/kvm_util.c +++ b/tools/testing/selftests/kvm/lib/kvm_util.c@@ -1354,6 +1354,13 @@ struct kvm_vcpu *__vm_vcpu_add(struct kvm_vm *vm, u32 vcpu_id) vcpu->vm = vm; vcpu->id = vcpu_id; vcpu->fd = __vm_ioctl(vm, KVM_CREATE_VCPU, (void *)(unsigned long)vcpu_id); + if (vcpu->fd < 0) { + int saved_errno = errno; + + pr_info("Failed KVM_CREATE_VCPU for vcpu_id %u with errno %d\n", + vcpu_id, saved_errno); + errno = saved_errno;
Sorry, but NAK. There are myriad failures where printing extra information can help debug a failure/assert, I don't want to create a slippery slope where the codebase is littered with extra print statements that someone found useful at some point.