Re: [PATCH v2 5/6] KVM: s390: Cap KVM_CAP_NR_VCPUS by num_online_cpus()

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Am 16.11.21 um 17:34 schrieb Vitaly Kuznetsov:
KVM_CAP_NR_VCPUS is a legacy advisory value which on other architectures
return num_online_cpus() caped by KVM_CAP_NR_VCPUS or something else
(ppc and arm64 are special cases). On s390, KVM_CAP_NR_VCPUS returns
the same as KVM_CAP_MAX_VCPUS and this may turn out to be a bad
'advice'. Switch s390 to returning caped num_online_cpus() too.

Acked-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>

you can also add
Reviewed-by: Christian Borntraeger <borntraeger@xxxxxxxxxxxxx>

(yes I am changing my default address, but the other should continue to work)

Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
  arch/s390/kvm/kvm-s390.c | 2 ++
  1 file changed, 2 insertions(+)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 6a6dd5e1daf6..1cfe36f6432e 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -585,6 +585,8 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
  			r = KVM_MAX_VCPUS;
  		else if (sclp.has_esca && sclp.has_64bscao)
  			r = KVM_S390_ESCA_CPU_SLOTS;
+		if (ext == KVM_CAP_NR_VCPUS)
+			r = min_t(unsigned int, num_online_cpus(), r);
  	case KVM_CAP_S390_COW:

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