arm/arm64: KVM: make the maximum number of vCPUs a per-VM value

Currently the maximum number of vCPUs supported is a global value
limited by the used GIC model. GICv3 will lift this limit, but we
still need to observe it for guests using GICv2.
So the maximum number of vCPUs is per-VM value, depending on the
GIC model the guest uses.
Store and check the value in struct kvm_arch, but keep it down to
8 for now.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

3 files changed, 12 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;