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Message-Id: <20211123163733.289925-1-sashal@kernel.org>
Date: Tue, 23 Nov 2021 11:37:32 -0500
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc: Vitaly Kuznetsov <vkuznets@...hat.com>,
Christian Borntraeger <borntraeger@...ibm.com>,
Christian Borntraeger <borntraeger@...ux.ibm.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Sasha Levin <sashal@...nel.org>, frankja@...ux.ibm.com,
hca@...ux.ibm.com, gor@...ux.ibm.com, kvm@...r.kernel.org,
linux-s390@...r.kernel.org
Subject: [PATCH MANUALSEL 4.9 1/2] KVM: s390: Cap KVM_CAP_NR_VCPUS by num_online_cpus()
From: Vitaly Kuznetsov <vkuznets@...hat.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@...ibm.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
Reviewed-by: Christian Borntraeger <borntraeger@...ux.ibm.com>
Message-Id: <20211116163443.88707-6-vkuznets@...hat.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.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
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