blob: 6c2ea758cde02cd19787a2b3e3620cdd26ba08c4 [file] [log] [blame]
From bbe5eea04a1d75b06e3102f915e84a5fb690c5b9 Mon Sep 17 00:00:00 2001
From: Sean Christopherson <>
Date: Thu, 27 Feb 2020 09:44:30 -0800
Subject: [PATCH] KVM: nVMX: Consult only the "basic" exit reason when routing
nested exit
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 <>
Cc: Xiaoyao Li <>
Signed-off-by: Sean Christopherson <>
Message-Id: <>
Signed-off-by: Paolo Bonzini <>
Signed-off-by: Paul Gortmaker <>
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 30f23f4b439e..c6deeed854f1 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -5125,7 +5125,7 @@ bool nested_vmx_exit_reflected(struct kvm_vcpu *vcpu, u32 exit_reason)
- switch (exit_reason) {
+ switch ((u16)exit_reason) {
if (is_nmi(intr_info))
return false;