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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: Kyle Huey <khuey@kylehuey.com>
Reviewed-by: David Matlack <dmatlack@google.com>
[Return "1" from kvm_emulate_cpuid, it's not void. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
hifive-unleashed-5.1
Kyle Huey 2017-03-20 01:16:28 -07:00 committed by Paolo Bonzini
parent bd17117bb2
commit db2336a804
5 changed files with 49 additions and 0 deletions
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2
arch/x86/include/asm/kvm_host.h
View File

@ -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;

3
arch/x86/kvm/cpuid.c
View File

@ -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);

11
arch/x86/kvm/cpuid.h
View File

@ -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

7
arch/x86/kvm/emulate.c
View File

@ -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);

26
arch/x86/kvm/x86.c
View File

@ -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));