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/svm.c | 28 ++++++++++++++++++++-------- 1 file changed, 20 insertions(+), 8 deletions(-) (limited to 'arch/x86/kvm/svm.c') diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 7f4f9c2..0b7d58d 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -2770,12 +2770,6 @@ static int xsetbv_interception(struct vcpu_svm *svm) return 1; } -static int invalid_op_interception(struct vcpu_svm *svm) -{ - kvm_queue_exception(&svm->vcpu, UD_VECTOR); - return 1; -} - static int task_switch_interception(struct vcpu_svm *svm) { u16 tss_selector; @@ -3287,6 +3281,24 @@ static int pause_interception(struct vcpu_svm *svm) return 1; } +static int nop_interception(struct vcpu_svm *svm) +{ + skip_emulated_instruction(&(svm->vcpu)); + return 1; +} + +static int monitor_interception(struct vcpu_svm *svm) +{ + printk_once(KERN_WARNING "kvm: MONITOR instruction emulated as NOP!\n"); + return nop_interception(svm); +} + +static int mwait_interception(struct vcpu_svm *svm) +{ + printk_once(KERN_WARNING "kvm: MWAIT instruction emulated as NOP!\n"); + return nop_interception(svm); +} + static int (*const svm_exit_handlers[])(struct vcpu_svm *svm) = { [SVM_EXIT_READ_CR0] = cr_interception, [SVM_EXIT_READ_CR3] = cr_interception, @@ -3344,8 +3356,8 @@ static int (*const svm_exit_handlers[])(struct vcpu_svm *svm) = { [SVM_EXIT_CLGI] = clgi_interception, [SVM_EXIT_SKINIT] = skinit_interception, [SVM_EXIT_WBINVD] = emulate_on_interception, - [SVM_EXIT_MONITOR] = invalid_op_interception, - [SVM_EXIT_MWAIT] = invalid_op_interception, + [SVM_EXIT_MONITOR] = monitor_interception, + [SVM_EXIT_MWAIT] = mwait_interception, [SVM_EXIT_XSETBV] = xsetbv_interception, [SVM_EXIT_NPF] = pf_interception, }; -- cgit v1.1