1 files changed, 37 insertions, 1 deletions

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index f56122eedffc..c0ffb019ca8b 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -102,6 +102,20 @@ static int kvm_arm_default_max_vcpus(void)
 	return vgic_present ? kvm_vgic_get_max_vcpus() : KVM_MAX_VCPUS;
 }
 
+static void set_default_csv2(struct kvm *kvm)
+{
+	/*
+	 * The default is to expose CSV2 == 1 if the HW isn't affected.
+	 * Although this is a per-CPU feature, we make it global because
+	 * asymmetric systems are just a nuisance.
+	 *
+	 * Userspace can override this as long as it doesn't promise
+	 * the impossible.
+	 */
+	if (arm64_get_spectre_v2_state() == SPECTRE_UNAFFECTED)
+		kvm->arch.pfr0_csv2 = 1;
+}
+
 /**
  * kvm_arch_init_vm - initializes a VM data structure
  * @kvm:	pointer to the KVM struct
@@ -127,6 +141,8 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 	/* The maximum number of VCPUs is limited by the host's GIC model */
 	kvm->arch.max_vcpus = kvm_arm_default_max_vcpus();
 
+	set_default_csv2(kvm);
+
 	return ret;
 out_free_stage2_pgd:
 	kvm_free_stage2_pgd(&kvm->arch.mmu);
@@ -808,6 +824,25 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
 
 		preempt_enable();
 
+		/*
+		 * The ARMv8 architecture doesn't give the hypervisor
+		 * a mechanism to prevent a guest from dropping to AArch32 EL0
+		 * if implemented by the CPU. If we spot the guest in such
+		 * state and that we decided it wasn't supposed to do so (like
+		 * with the asymmetric AArch32 case), return to userspace with
+		 * a fatal error.
+		 */
+		if (!system_supports_32bit_el0() && vcpu_mode_is_32bit(vcpu)) {
+			/*
+			 * As we have caught the guest red-handed, decide that
+			 * it isn't fit for purpose anymore by making the vcpu
+			 * invalid. The VMM can try and fix it by issuing  a
+			 * KVM_ARM_VCPU_INIT if it really wants to.
+			 */
+			vcpu->arch.target = -1;
+			ret = ARM_EXCEPTION_IL;
+		}
+
 		ret = handle_exit(vcpu, ret);
 	}
 
@@ -1719,7 +1754,8 @@ int kvm_arch_init(void *opaque)
 		return -ENODEV;
 	}
 
-	if (cpus_have_final_cap(ARM64_WORKAROUND_DEVICE_LOAD_ACQUIRE))
+	if (cpus_have_final_cap(ARM64_WORKAROUND_DEVICE_LOAD_ACQUIRE) ||
+	    cpus_have_final_cap(ARM64_WORKAROUND_1508412))
 		kvm_info("Guests without required CPU erratum workarounds can deadlock system!\n" \
 			 "Only trusted guests should be used on this system.\n");