7 files changed, 38 insertions, 0 deletions

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 2fa51740edc2..bde494654bcc 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -68,6 +68,7 @@ struct kvm_arch {
 
         /* Interrupt controller */
         struct vgic_dist        vgic;
+        int max_vcpus;
 };
 
 #define KVM_NR_MEM_OBJS     40
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 3a51ffca75e3..6fbfa5fff05d 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -132,6 +132,9 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
         /* Mark the initial VMID generation invalid */
         kvm->arch.vmid_gen = 0;
 
+        /* The maximum number of VCPUs is limited by the host's GIC model */
+        kvm->arch.max_vcpus = kvm_vgic_get_max_vcpus();
+
         return ret;
 out_free_stage2_pgd:
         kvm_free_stage2_pgd(kvm);
@@ -218,6 +221,11 @@ struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm, unsigned int id)
                 goto out;
         }
 
+        if (id >= kvm->arch.max_vcpus) {
+                err = -EINVAL;
+                goto out;
+        }
+
         vcpu = kmem_cache_zalloc(kvm_vcpu_cache, GFP_KERNEL);
         if (!vcpu) {
                 err = -ENOMEM;
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index ff8ee3ec32f4..2c49aa4ac818 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -59,6 +59,9 @@ struct kvm_arch {
         /* VTTBR value associated with above pgd and vmid */
         u64    vttbr;
 
+        /* The maximum number of vCPUs depends on the used GIC model */
+        int max_vcpus;
+
         /* Interrupt controller */
         struct vgic_dist        vgic;
 
diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index dd243969bfc3..1c0e9dbabe6d 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -33,6 +33,7 @@
 #define VGIC_V2_MAX_LRS         (1 << 6)
 #define VGIC_V3_MAX_LRS         16
 #define VGIC_MAX_IRQS           1024
+#define VGIC_V2_MAX_CPUS        8
 
 /* Sanity checks... */
 #if (KVM_MAX_VCPUS > 8)
@@ -132,6 +133,7 @@ struct vgic_params {
         unsigned int    maint_irq;
         /* Virtual control interface base address */
         void __iomem    *vctrl_base;
+        int             max_gic_vcpus;
 };
 
 struct vgic_vm_ops {
@@ -289,6 +291,7 @@ struct kvm_exit_mmio;
 int kvm_vgic_addr(struct kvm *kvm, unsigned long type, u64 *addr, bool write);
 int kvm_vgic_hyp_init(void);
 int kvm_vgic_map_resources(struct kvm *kvm);
+int kvm_vgic_get_max_vcpus(void);
 int kvm_vgic_create(struct kvm *kvm, u32 type);
 void kvm_vgic_destroy(struct kvm *kvm);
 void kvm_vgic_vcpu_destroy(struct kvm_vcpu *vcpu);
@@ -393,6 +396,11 @@ static inline bool vgic_ready(struct kvm *kvm)
 {
         return true;
 }
+
+static inline int kvm_vgic_get_max_vcpus(void)
+{
+        return KVM_MAX_VCPUS;
+}
 #endif
 
 #endif
diff --git a/virt/kvm/arm/vgic-v2.c b/virt/kvm/arm/vgic-v2.c
index e1cd3cb95903..e8b82b289844 100644
--- a/virt/kvm/arm/vgic-v2.c
+++ b/virt/kvm/arm/vgic-v2.c
@@ -237,6 +237,7 @@ int vgic_v2_probe(struct device_node *vgic_node,
                  vctrl_res.start, vgic->maint_irq);
 
         vgic->type = VGIC_V2;
+        vgic->max_gic_vcpus = VGIC_V2_MAX_CPUS;
         *ops = &vgic_v2_ops;
         *params = vgic;
         goto out;
diff --git a/virt/kvm/arm/vgic-v3.c b/virt/kvm/arm/vgic-v3.c
index d14c75f4a33b..ea39bad4b004 100644
--- a/virt/kvm/arm/vgic-v3.c
+++ b/virt/kvm/arm/vgic-v3.c
@@ -235,6 +235,7 @@ int vgic_v3_probe(struct device_node *vgic_node,
         vgic->vcpu_base = vcpu_res.start;
         vgic->vctrl_base = NULL;
         vgic->type = VGIC_V3;
+        vgic->max_gic_vcpus = KVM_MAX_VCPUS;
 
         kvm_info("%s@%llx IRQ%d\n", vgic_node->name,
                  vcpu_res.start, vgic->maint_irq);
diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
index 1c3b75eb28f0..2126bf5b0035 100644
--- a/virt/kvm/arm/vgic.c
+++ b/virt/kvm/arm/vgic.c
@@ -1878,6 +1878,17 @@ static int vgic_vcpu_init_maps(struct kvm_vcpu *vcpu, int nr_irqs)
         return 0;
 }
 
+/**
+ * kvm_vgic_get_max_vcpus - Get the maximum number of VCPUs allowed by HW
+ *
+ * The host's GIC naturally limits the maximum amount of VCPUs a guest
+ * can use.
+ */
+int kvm_vgic_get_max_vcpus(void)
+{
+        return vgic->max_gic_vcpus;
+}
+
 void kvm_vgic_destroy(struct kvm *kvm)
 {
         struct vgic_dist *dist = &kvm->arch.vgic;
@@ -2072,6 +2083,8 @@ static void vgic_v2_init_emulation(struct kvm *kvm)
         dist->vm_ops.add_sgi_source = vgic_v2_add_sgi_source;
         dist->vm_ops.init_model = vgic_v2_init_model;
         dist->vm_ops.map_resources = vgic_v2_map_resources;
+
+        kvm->arch.max_vcpus = VGIC_V2_MAX_CPUS;
 }
 
 static int init_vgic_model(struct kvm *kvm, int type)
@@ -2084,6 +2097,9 @@ static int init_vgic_model(struct kvm *kvm, int type)
                 return -ENODEV;
         }
 
+        if (atomic_read(&kvm->online_vcpus) > kvm->arch.max_vcpus)
+                return -E2BIG;
+
         return 0;
 }