From a86cb413f4bf273a9d341a3ab2c2ca44e12eb317 Mon Sep 17 00:00:00 2001 From: Thomas Huth Date: Thu, 23 May 2019 18:43:08 +0200 Subject: KVM: s390: Do not report unusabled IDs via KVM_CAP_MAX_VCPU_ID KVM_CAP_MAX_VCPU_ID is currently always reporting KVM_MAX_VCPU_ID on all architectures. However, on s390x, the amount of usable CPUs is determined during runtime - it is depending on the features of the machine the code is running on. Since we are using the vcpu_id as an index into the SCA structures that are defined by the hardware (see e.g. the sca_add_vcpu() function), it is not only the amount of CPUs that is limited by the hard- ware, but also the range of IDs that we can use. Thus KVM_CAP_MAX_VCPU_ID must be determined during runtime on s390x, too. So the handling of KVM_CAP_MAX_VCPU_ID has to be moved from the common code into the architecture specific code, and on s390x we have to return the same value here as for KVM_CAP_MAX_VCPUS. This problem has been discovered with the kvm_create_max_vcpus selftest. With this change applied, the selftest now passes on s390x, too. Reviewed-by: Andrew Jones Reviewed-by: Cornelia Huck Reviewed-by: David Hildenbrand Signed-off-by: Thomas Huth Message-Id: <20190523164309.13345-9-thuth@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: Christian Borntraeger --- arch/s390/kvm/kvm-s390.c | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/s390/kvm') diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index e5e8eb29e68e..28ebd647784c 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -539,6 +539,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) break; case KVM_CAP_NR_VCPUS: case KVM_CAP_MAX_VCPUS: + case KVM_CAP_MAX_VCPU_ID: r = KVM_S390_BSCA_CPU_SLOTS; if (!kvm_s390_use_sca_entries()) r = KVM_MAX_VCPUS; -- cgit v1.2.3-59-g8ed1b