Re: [RFC PATCH v5 022/104] KVM: Add max_vcpus field in common 'struct kvm'

[Paolo Bonzini]

On 3/4/22 20:48, isaku.yamahata@xxxxxxxxx wrote:
> From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
>
> For TDX guests, the maximum number of vcpus needs to be specified when the
> TDX guest VM is initialized (creating the TDX data corresponding to TDX
> guest) before creating vcpu.  It needs to record the maximum number of
> vcpus on VM creation (KVM_CREATE_VM) and return error if the number of
> vcpus exceeds it
>
> Because there is already max_vcpu member in arm64 struct kvm_arch, move it
> to common struct kvm and initialize it to KVM_MAX_VCPUS before
> kvm_arch_init_vm() instead of adding it to x86 struct kvm_arch.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> ---
>   arch/arm64/include/asm/kvm_host.h | 3 ---
>   arch/arm64/kvm/arm.c              | 6 +++---
>   arch/arm64/kvm/vgic/vgic-init.c   | 6 +++---
>   include/linux/kvm_host.h          | 1 +
>   virt/kvm/kvm_main.c               | 3 ++-
>   5 files changed, 9 insertions(+), 10 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 5bc01e62c08a..27249d634605 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -107,9 +107,6 @@ 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 ecc5958e27fe..defec2cd94bd 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -153,7 +153,7 @@ 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);
>   
> @@ -229,7 +229,7 @@ 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;
> @@ -305,7 +305,7 @@ 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)
> +	if (id >= kvm->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 fc00304fe7d8..77feafd5c0e3 100644
> --- a/arch/arm64/kvm/vgic/vgic-init.c
> +++ b/arch/arm64/kvm/vgic/vgic-init.c
> @@ -98,11 +98,11 @@ 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 f11039944c08..a56044a31bc6 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -715,6 +715,7 @@ 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 52f72a366beb..3adee9c6b370 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -1075,6 +1075,7 @@ static struct kvm *kvm_create_vm(unsigned long type)
>   	spin_lock_init(&kvm->gpc_lock);
>   
>   	INIT_LIST_HEAD(&kvm->devices);
> +	kvm->max_vcpus = KVM_MAX_VCPUS;
>   
>   	BUILD_BUG_ON(KVM_MEM_SLOTS_NUM > SHRT_MAX);
>   
> @@ -3718,7 +3719,7 @@ 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;
>   	}

Queued this one already, thanks.

Paolo