Commit 2bb8cafe authored Mar 12, 2018 by Sean Christopherson Committed by Paolo Bonzini Mar 16, 2018

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>

parent e1de91cc

arch/x86/kvm/vmx.c

+15 −0

Original line number	Diff line number	Diff line
		@@ -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))