From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vitaly Kuznetsov Date: Tue, 16 Nov 2021 16:34:38 +0000 Subject: [PATCH v2 1/6] KVM: arm64: Cap KVM_CAP_NR_VCPUS by kvm_arm_default_max_vcpus() Message-Id: <20211116163443.88707-2-vkuznets@redhat.com> List-Id: References: <20211116163443.88707-1-vkuznets@redhat.com> In-Reply-To: <20211116163443.88707-1-vkuznets@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: kvm@vger.kernel.org, Paolo Bonzini Cc: Sean Christopherson , Wanpeng Li , Jim Mattson , Eduardo Habkost , Marc Zyngier , Andrew Jones , Huacai Chen , Aleksandar Markovic , Anup Patel , Paul Mackerras , Michael Ellerman , Christian Borntraeger , Janosch Frank , 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 Generally, it doesn't make sense to return the recommended maximum number of vCPUs which exceeds the maximum possible number of vCPUs. Note: ARM64 is special as the value returned by KVM_CAP_MAX_VCPUS differs depending on whether it is a system-wide ioctl or a per-VM one. Previously, KVM_CAP_NR_VCPUS didn't have this difference and it seems preferable to keep the status quo. Cap KVM_CAP_NR_VCPUS by kvm_arm_default_max_vcpus() which is what gets returned by system-wide KVM_CAP_MAX_VCPUS. Signed-off-by: Vitaly Kuznetsov --- arch/arm64/kvm/arm.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index 7838e9fb693e..0690c76def5d 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -223,7 +223,14 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) r = 1; break; case KVM_CAP_NR_VCPUS: - r = num_online_cpus(); + /* + * ARM64 treats KVM_CAP_NR_CPUS differently from all other + * architectures, as it does not always bound it to + * num_online_cpus(). It should not matter much because this + * is just an advisory value. + */ + r = min_t(unsigned int, num_online_cpus(), + kvm_arm_default_max_vcpus()); break; case KVM_CAP_MAX_VCPUS: case KVM_CAP_MAX_VCPU_ID: -- 2.33.1