[PATCH] KVM: Add max_vcpus field in common 'struct kvm'

[Sean Christopherson]

Move arm's per-VM max_vcpus field into the generic "struct kvm", and use
it to check vcpus_created in the generic code instead of checking only
the hardcoded absolute KVM-wide max.  x86 TDX guests will reuse the
generic check verbatim, as the max number of vCPUs for a TDX guest is
user defined at VM creation and immutable thereafter.

Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
 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 4be8486042a7..b51e1aa6ae27 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -108,9 +108,6 @@ 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 f5490afe1ebf..97c3b83235b4 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);

@@ -228,7 +228,7 @@ 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;
@@ -304,9 +304,6 @@ 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 0a06d0648970..906aee52f2bc 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 60a35d9fe259..5f56516e2f5a 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -566,6 +566,7 @@ 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 3f6d450355f0..e509b963651c 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1052,6 +1052,7 @@ static struct kvm *kvm_create_vm(unsigned long type)
 	rcuwait_init(&kvm->mn_memslots_update_rcuwait);

 	INIT_LIST_HEAD(&kvm->devices);
+	kvm->max_vcpus = KVM_MAX_VCPUS;

 	BUILD_BUG_ON(KVM_MEM_SLOTS_NUM > SHRT_MAX);

@@ -3599,7 +3600,7 @@ 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;
 	}
--
2.34.0.rc1.387.gb447b232ab-goog