From:   Vitaly Kuznetsov <vkuznets@redhat.com>
To:     kvm@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>
Cc:     Sean Christopherson <seanjc@google.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Eduardo Habkost <ehabkost@redhat.com>,
        Marc Zyngier <maz@kernel.org>,
        Andrew Jones <drjones@redhat.com>,
        Huacai Chen <chenhuacai@kernel.org>,
        Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>,
        Anup Patel <anup.patel@wdc.com>,
        Paul Mackerras <paulus@ozlabs.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        Janosch Frank <frankja@linux.ibm.com>, kvm-ppc@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org,
        kvm-riscv@lists.infradead.org, linux-s390@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH v2 5/6] KVM: s390: Cap KVM_CAP_NR_VCPUS by num_online_cpus()
Date:   Tue, 16 Nov 2021 17:34:42 +0100
Message-Id: <20211116163443.88707-6-vkuznets@redhat.com>
In-Reply-To: <20211116163443.88707-1-vkuznets@redhat.com>
References: <20211116163443.88707-1-vkuznets@redhat.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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@de.ibm.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 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);
 		break;
 	case KVM_CAP_S390_COW:
 		r = MACHINE_HAS_ESOP;
-- 
2.33.1