Commit 2ebac8bb authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini

KVM: nVMX: Consult only the "basic" exit reason when routing nested exit

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: 644d711a ("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: default avatarSean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200227174430.26371-1-sean.j.christopherson@intel.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 3d77e6a8
......@@ -5577,7 +5577,7 @@ bool nested_vmx_exit_reflected(struct kvm_vcpu *vcpu, u32 exit_reason)
vmcs_read32(VM_EXIT_INTR_ERROR_CODE),
KVM_ISA_VMX);
switch (exit_reason) {
switch ((u16)exit_reason) {
case EXIT_REASON_EXCEPTION_NMI:
if (is_nmi(intr_info))
return false;
......
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