From 87c00572ba05aa8c9db118da75c608f47eb10b9e Mon Sep 17 00:00:00 2001 From: "Gabriel L. Somlo" Date: Wed, 7 May 2014 16:52:13 -0400 Subject: 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 Signed-off-by: Paolo Bonzini --- arch/x86/kvm/cpuid.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'arch/x86/kvm/cpuid.c') diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 17b42fabc842..38a0afe83c6b 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -283,6 +283,8 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function, 0 /* Reserved */ | f_lm | F(3DNOWEXT) | F(3DNOW); /* cpuid 1.ecx */ const u32 kvm_supported_word4_x86_features = + /* NOTE: MONITOR (and MWAIT) are emulated as NOP, + * but *not* advertised to guests via CPUID ! */ F(XMM3) | F(PCLMULQDQ) | 0 /* DTES64, MONITOR */ | 0 /* DS-CPL, VMX, SMX, EST */ | 0 /* TM2 */ | F(SSSE3) | 0 /* CNXT-ID */ | 0 /* Reserved */ | -- cgit v1.2.3