Commit db2336a8 authored by Kyle Huey's avatar Kyle Huey Committed by Paolo Bonzini
Browse files

KVM: x86: virtualize cpuid faulting 



Hardware support for faulting on the cpuid instruction is not required to
emulate it, because cpuid triggers a VM exit anyways. KVM handles the relevant
MSRs (MSR_PLATFORM_INFO and MSR_MISC_FEATURES_ENABLE) and upon a
cpuid-induced VM exit checks the cpuid faulting state and the CPL.
kvm_require_cpl is even kind enough to inject the GP fault for us.

Signed-off-by: default avatarKyle Huey <khuey@kylehuey.com>
Reviewed-by: default avatarDavid Matlack <dmatlack@google.com>
[Return "1" from kvm_emulate_cpuid, it's not void. - Paolo]
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent bd17117b

arch/x86/include/asm/kvm_host.h

+2 −0
Original line number Diff line number Diff line
@@ -611,6 +611,8 @@ struct kvm_vcpu_arch { 
	unsigned long dr7;

	unsigned long eff_db[KVM_NR_DB_REGS];

	unsigned long guest_debug_dr7;

	u64 msr_platform_info;

	u64 msr_misc_features_enables;



	u64 mcg_cap;

	u64 mcg_status;

arch/x86/kvm/cpuid.c

+3 −0
Original line number Diff line number Diff line
@@ -876,6 +876,9 @@ int kvm_emulate_cpuid(struct kvm_vcpu *vcpu) 
{

	u32 eax, ebx, ecx, edx;



	if (cpuid_fault_enabled(vcpu) && !kvm_require_cpl(vcpu, 0))

		return 1;



	eax = kvm_register_read(vcpu, VCPU_REGS_RAX);

	ecx = kvm_register_read(vcpu, VCPU_REGS_RCX);

	kvm_cpuid(vcpu, &eax, &ebx, &ecx, &edx);

arch/x86/kvm/cpuid.h

+11 −0
Original line number Diff line number Diff line
@@ -205,4 +205,15 @@ static inline int guest_cpuid_stepping(struct kvm_vcpu *vcpu) 
	return x86_stepping(best->eax);

}



static inline bool supports_cpuid_fault(struct kvm_vcpu *vcpu)

{

	return vcpu->arch.msr_platform_info & MSR_PLATFORM_INFO_CPUID_FAULT;

}



static inline bool cpuid_fault_enabled(struct kvm_vcpu *vcpu)

{

	return vcpu->arch.msr_misc_features_enables &

		  MSR_MISC_FEATURES_ENABLES_CPUID_FAULT;

}



#endif

arch/x86/kvm/emulate.c

+7 −0
Original line number Diff line number Diff line
@@ -3854,6 +3854,13 @@ static int em_sti(struct x86_emulate_ctxt *ctxt) 
static int em_cpuid(struct x86_emulate_ctxt *ctxt)

{

	u32 eax, ebx, ecx, edx;

	u64 msr = 0;



	ctxt->ops->get_msr(ctxt, MSR_MISC_FEATURES_ENABLES, &msr);

	if (msr & MSR_MISC_FEATURES_ENABLES_CPUID_FAULT &&

	    ctxt->ops->cpl(ctxt)) {

		return emulate_gp(ctxt, 0);

	}



	eax = reg_read(ctxt, VCPU_REGS_RAX);

	ecx = reg_read(ctxt, VCPU_REGS_RCX);

arch/x86/kvm/x86.c

+26 −0
Original line number Diff line number Diff line
@@ -1007,6 +1007,8 @@ static u32 emulated_msrs[] = { 
	MSR_IA32_MCG_CTL,

	MSR_IA32_MCG_EXT_CTL,

	MSR_IA32_SMBASE,

	MSR_PLATFORM_INFO,

	MSR_MISC_FEATURES_ENABLES,

};



static unsigned num_emulated_msrs;
@@ -2314,6 +2316,21 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) 
			return 1;

		vcpu->arch.osvw.status = data;

		break;

	case MSR_PLATFORM_INFO:

		if (!msr_info->host_initiated ||

		    data & ~MSR_PLATFORM_INFO_CPUID_FAULT ||

		    (!(data & MSR_PLATFORM_INFO_CPUID_FAULT) &&

		     cpuid_fault_enabled(vcpu)))

			return 1;

		vcpu->arch.msr_platform_info = data;

		break;

	case MSR_MISC_FEATURES_ENABLES:

		if (data & ~MSR_MISC_FEATURES_ENABLES_CPUID_FAULT ||

		    (data & MSR_MISC_FEATURES_ENABLES_CPUID_FAULT &&

		     !supports_cpuid_fault(vcpu)))

			return 1;

		vcpu->arch.msr_misc_features_enables = data;

		break;

	default:

		if (msr && (msr == vcpu->kvm->arch.xen_hvm_config.msr))

			return xen_hvm_config(vcpu, data);
@@ -2529,6 +2546,12 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) 
			return 1;

		msr_info->data = vcpu->arch.osvw.status;

		break;

	case MSR_PLATFORM_INFO:

		msr_info->data = vcpu->arch.msr_platform_info;

		break;

	case MSR_MISC_FEATURES_ENABLES:

		msr_info->data = vcpu->arch.msr_misc_features_enables;

		break;

	default:

		if (kvm_pmu_is_valid_msr(vcpu, msr_info->index))

			return kvm_pmu_get_msr(vcpu, msr_info->index, &msr_info->data);
@@ -7710,6 +7733,9 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) 
	if (!init_event) {

		kvm_pmu_reset(vcpu);

		vcpu->arch.smbase = 0x30000;



		vcpu->arch.msr_platform_info = MSR_PLATFORM_INFO_CPUID_FAULT;

		vcpu->arch.msr_misc_features_enables = 0;

	}



	memset(vcpu->arch.regs, 0, sizeof(vcpu->arch.regs));

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