[PATCH MANUALSEL 4.9 1/2] KVM: s390: Cap KVM_CAP_NR_VCPUS by num_online_cpus()

[PATCH MANUALSEL 4.9 1/2] KVM: s390: Cap KVM_CAP_NR_VCPUS by num_online_cpus()

[Sasha Levin]

From: Vitaly Kuznetsov <vkuznets@redhat.com>

[ Upstream commit 82cc27eff4486f8e79ef8faac1af1f5573039aa4 ]

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>
Reviewed-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Message-Id: <20211116163443.88707-6-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 d8fd2eadcda7f..b8f67d19e132d 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -399,6 +399,8 @@ 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_NR_MEMSLOTS:
 		r = KVM_USER_MEM_SLOTS;
-- 
2.33.0

[PATCH MANUALSEL 4.9 2/2] KVM: PPC: Cap KVM_CAP_NR_VCPUS by KVM_CAP_MAX_VCPUS

[Sasha Levin]

From: Vitaly Kuznetsov <vkuznets@redhat.com>

[ Upstream commit b7915d55b1ac0e68a7586697fa2d06c018135c49 ]

It doesn't make sense to return the recommended maximum number of
vCPUs which exceeds the maximum possible number of vCPUs.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20211116163443.88707-4-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/powerpc/kvm/powerpc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index fc0df0f6fe881..596c7612bbbff 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -582,9 +582,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 		 * implementations just count online CPUs.
 		 */
 		if (hv_enabled)
-			r = num_present_cpus();
+			r = min_t(unsigned int, num_present_cpus(), KVM_MAX_VCPUS);
 		else
-			r = num_online_cpus();
+			r = min_t(unsigned int, num_online_cpus(), KVM_MAX_VCPUS);
 		break;
 	case KVM_CAP_NR_MEMSLOTS:
 		r = KVM_USER_MEM_SLOTS;
-- 
2.33.0