kvm: x86: emulate monitor and mwait instructions as nop
Treat monitor and mwait instructions as nop, which is architecturally
correct (but inefficient) behavior. We do this to prevent misbehaving
guests (e.g. OS X <= 10.7) from crashing after they fail to check for
monitor/mwait availability via cpuid.
Since mwait-based idle loops relying on these nop-emulated instructions
would keep the host CPU pegged at 100%, do NOT advertise their presence
via cpuid, to prevent compliant guests from using them inadvertently.
Signed-off-by: Gabriel L. Somlo <somlo@cmu.edu>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 61e818d..6f7463f 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -5650,12 +5650,24 @@
return 1;
}
-static int handle_invalid_op(struct kvm_vcpu *vcpu)
+static int handle_nop(struct kvm_vcpu *vcpu)
{
- kvm_queue_exception(vcpu, UD_VECTOR);
+ skip_emulated_instruction(vcpu);
return 1;
}
+static int handle_mwait(struct kvm_vcpu *vcpu)
+{
+ printk_once(KERN_WARNING "kvm: MWAIT instruction emulated as NOP!\n");
+ return handle_nop(vcpu);
+}
+
+static int handle_monitor(struct kvm_vcpu *vcpu)
+{
+ printk_once(KERN_WARNING "kvm: MONITOR instruction emulated as NOP!\n");
+ return handle_nop(vcpu);
+}
+
/*
* To run an L2 guest, we need a vmcs02 based on the L1-specified vmcs12.
* We could reuse a single VMCS for all the L2 guests, but we also want the
@@ -6617,8 +6629,8 @@
[EXIT_REASON_EPT_VIOLATION] = handle_ept_violation,
[EXIT_REASON_EPT_MISCONFIG] = handle_ept_misconfig,
[EXIT_REASON_PAUSE_INSTRUCTION] = handle_pause,
- [EXIT_REASON_MWAIT_INSTRUCTION] = handle_invalid_op,
- [EXIT_REASON_MONITOR_INSTRUCTION] = handle_invalid_op,
+ [EXIT_REASON_MWAIT_INSTRUCTION] = handle_mwait,
+ [EXIT_REASON_MONITOR_INSTRUCTION] = handle_monitor,
[EXIT_REASON_INVEPT] = handle_invept,
};
