From: Sean Christopherson sean.j.christopherson@intel.com
commit 2ebac8bb3c2d35f5135466490fc8eeaf3f3e2d37 upstream.
Consult only the basic exit reason, i.e. bits 15:0 of vmcs.EXIT_REASON, when determining whether a nested VM-Exit should be reflected into L1 or handled by KVM in L0.
For better or worse, the switch statement in nested_vmx_exit_reflected() currently defaults to "true", i.e. reflects any nested VM-Exit without dedicated logic. Because the case statements only contain the basic exit reason, any VM-Exit with modifier bits set will be reflected to L1, even if KVM intended to handle it in L0.
Practically speaking, this only affects EXIT_REASON_MCE_DURING_VMENTRY, i.e. a #MC that occurs on nested VM-Enter would be incorrectly routed to L1, as "failed VM-Entry" is the only modifier that KVM can currently encounter. The SMM modifiers will never be generated as KVM doesn't support/employ a SMI Transfer Monitor. Ditto for "exit from enclave", as KVM doesn't yet support virtualizing SGX, i.e. it's impossible to enter an enclave in a KVM guest (L1 or L2).
Fixes: 644d711aa0e1 ("KVM: nVMX: Deciding if L0 or L1 should handle an L2 exit") Cc: Jim Mattson jmattson@google.com Cc: Xiaoyao Li xiaoyao.li@intel.com Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson sean.j.christopherson@intel.com Message-Id: 20200227174430.26371-1-sean.j.christopherson@intel.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/kvm/vmx.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -7844,7 +7844,7 @@ static bool nested_vmx_exit_handled(stru return true; }
- switch (exit_reason) { + switch ((u16)exit_reason) { case EXIT_REASON_EXCEPTION_NMI: if (is_nmi(intr_info)) return false;