linux-kernel - Re: [RFC PATCH v2 21/69] KVM: Add max_vcpus field in common 'struct kvm'

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Date:   Tue, 6 Jul 2021 15:49:07 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     isaku.yamahata@...el.com, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, erdemaktas@...gle.com,
        Connor Kuehl <ckuehl@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     isaku.yamahata@...il.com,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: Re: [RFC PATCH v2 21/69] KVM: Add max_vcpus field in common 'struct
 kvm'

Please replace "Add" with "Move" and add a couple lines to the commit 
message.

Paolo

On 03/07/21 00:04, isaku.yamahata@...el.com wrote:
> From: Sean Christopherson <sean.j.christopherson@...el.com>
> 
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> ---
>   arch/arm64/include/asm/kvm_host.h | 3 ---
>   arch/arm64/kvm/arm.c              | 7 ++-----
>   arch/arm64/kvm/vgic/vgic-init.c   | 6 +++---
>   include/linux/kvm_host.h          | 1 +
>   virt/kvm/kvm_main.c               | 3 ++-
>   5 files changed, 8 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 7cd7d5c8c4bc..96a0dc3a8780 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -106,9 +106,6 @@ struct kvm_arch {
>   	/* VTCR_EL2 value for this VM */
>   	u64    vtcr;
>   
> -	/* The maximum number of vCPUs depends on the used GIC model */
> -	int max_vcpus;
> -
>   	/* Interrupt controller */
>   	struct vgic_dist	vgic;
>   
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index e720148232a0..a46306cf3106 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -145,7 +145,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
>   	kvm_vgic_early_init(kvm);
>   
>   	/* The maximum number of VCPUs is limited by the host's GIC model */
> -	kvm->arch.max_vcpus = kvm_arm_default_max_vcpus();
> +	kvm->max_vcpus = kvm_arm_default_max_vcpus();
>   
>   	set_default_spectre(kvm);
>   
> @@ -220,7 +220,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>   	case KVM_CAP_MAX_VCPUS:
>   	case KVM_CAP_MAX_VCPU_ID:
>   		if (kvm)
> -			r = kvm->arch.max_vcpus;
> +			r = kvm->max_vcpus;
>   		else
>   			r = kvm_arm_default_max_vcpus();
>   		break;
> @@ -299,9 +299,6 @@ int kvm_arch_vcpu_precreate(struct kvm *kvm, unsigned int id)
>   	if (irqchip_in_kernel(kvm) && vgic_initialized(kvm))
>   		return -EBUSY;
>   
> -	if (id >= kvm->arch.max_vcpus)
> -		return -EINVAL;
> -
>   	return 0;
>   }
>   
> diff --git a/arch/arm64/kvm/vgic/vgic-init.c b/arch/arm64/kvm/vgic/vgic-init.c
> index 58cbda00e56d..089ac00c55d7 100644
> --- a/arch/arm64/kvm/vgic/vgic-init.c
> +++ b/arch/arm64/kvm/vgic/vgic-init.c
> @@ -97,11 +97,11 @@ int kvm_vgic_create(struct kvm *kvm, u32 type)
>   	ret = 0;
>   
>   	if (type == KVM_DEV_TYPE_ARM_VGIC_V2)
> -		kvm->arch.max_vcpus = VGIC_V2_MAX_CPUS;
> +		kvm->max_vcpus = VGIC_V2_MAX_CPUS;
>   	else
> -		kvm->arch.max_vcpus = VGIC_V3_MAX_CPUS;
> +		kvm->max_vcpus = VGIC_V3_MAX_CPUS;
>   
> -	if (atomic_read(&kvm->online_vcpus) > kvm->arch.max_vcpus) {
> +	if (atomic_read(&kvm->online_vcpus) > kvm->max_vcpus) {
>   		ret = -E2BIG;
>   		goto out_unlock;
>   	}
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index e87f07c5c601..ddd4d0f68cdf 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -544,6 +544,7 @@ struct kvm {
>   	 * and is accessed atomically.
>   	 */
>   	atomic_t online_vcpus;
> +	int max_vcpus;
>   	int created_vcpus;
>   	int last_boosted_vcpu;
>   	struct list_head vm_list;
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index dc752d0bd3ec..52d40ea75749 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -910,6 +910,7 @@ static struct kvm *kvm_create_vm(unsigned long type)
>   	mutex_init(&kvm->irq_lock);
>   	mutex_init(&kvm->slots_lock);
>   	INIT_LIST_HEAD(&kvm->devices);
> +	kvm->max_vcpus = KVM_MAX_VCPUS;
>   
>   	BUILD_BUG_ON(KVM_MEM_SLOTS_NUM > SHRT_MAX);
>   
> @@ -3329,7 +3330,7 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id)
>   		return -EINVAL;
>   
>   	mutex_lock(&kvm->lock);
> -	if (kvm->created_vcpus == KVM_MAX_VCPUS) {
> +	if (kvm->created_vcpus >= kvm->max_vcpus) {
>   		mutex_unlock(&kvm->lock);
>   		return -EINVAL;
>   	}
>