linux-kernel - [PATCH MANUALSEL 5.10 2/5] KVM: s390: Cap KVM_CAP_NR_VCPUS by num_online

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20211123163652.289483-2-sashal@kernel.org>
Date:   Tue, 23 Nov 2021 11:36:46 -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 5.10 2/5] 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 00f03f363c9b0..25ca18ed07bdc 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -564,6 +564,8 @@ 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;
-- 
2.33.0