From 2bb8cafea80bf69c0e729bf1ad1bcd1d6c53248d Mon Sep 17 00:00:00 2001 From: Sean Christopherson <sean.j.christopherson@intel.com> Date: Mon, 12 Mar 2018 10:56:13 -0700 Subject: [PATCH] KVM: vVMX: signal failure for nested VMEntry if emulation_required Fail a nested VMEntry with EXIT_REASON_INVALID_STATE if L2 guest state is invalid, i.e. vmcs12 contained invalid guest state, and unrestricted guest is disabled in L0 (and by extension disabled in L1). WARN_ON_ONCE in handle_invalid_guest_state() if we're attempting to emulate L2, i.e. nested_run_pending is true, to aid debug in the (hopefully unlikely) scenario that we somehow skip the nested VMEntry consistency check, e.g. due to a L0 bug. Note: KVM relies on hardware to detect the scenario where unrestricted guest is enabled in L0 but disabled in L1 and vmcs12 contains invalid guest state, i.e. checking emulation_required in prepare_vmcs02 is required only to handle the case were unrestricted guest is disabled in L0 since L0 never actually attempts VMLAUNCH/VMRESUME with vmcs02. Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> --- arch/x86/kvm/vmx.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 6cefd7b3ff7f..5d67a15b5116 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -6865,6 +6865,13 @@ static int handle_invalid_guest_state(struct kvm_vcpu *vcpu) bool intr_window_requested; unsigned count = 130; + /* + * We should never reach the point where we are emulating L2 + * due to invalid guest state as that means we incorrectly + * allowed a nested VMEntry with an invalid vmcs12. + */ + WARN_ON_ONCE(vmx->emulation_required && vmx->nested.nested_run_pending); + cpu_exec_ctrl = vmcs_read32(CPU_BASED_VM_EXEC_CONTROL); intr_window_requested = cpu_exec_ctrl & CPU_BASED_VIRTUAL_INTR_PENDING; @@ -10990,6 +10997,14 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12, vmx->nested.dirty_vmcs12 = false; } + /* + * Guest state is invalid and unrestricted guest is disabled, + * which means L1 attempted VMEntry to L2 with invalid state. + * Fail the VMEntry. + */ + if (vmx->emulation_required) + return 1; + /* Shadow page tables on either EPT or shadow page tables. */ if (nested_vmx_load_cr3(vcpu, vmcs12->guest_cr3, nested_cpu_has_ept(vmcs12), entry_failure_code)) -- GitLab