[PATCH v12 7/7] KVM: x86: virtualize cpuid faulting
From: Kyle Huey
Date: Wed Nov 16 2016 - 21:06:56 EST
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@xxxxxxxxxxxx>
Reviewed-by: David Matlack <dmatlack@xxxxxxxxxx>
---
arch/x86/include/asm/kvm_host.h | 2 ++
arch/x86/kvm/cpuid.c | 3 +++
arch/x86/kvm/cpuid.h | 11 +++++++++++
arch/x86/kvm/emulate.c | 7 +++++++
arch/x86/kvm/x86.c | 26 ++++++++++++++++++++++++++
5 files changed, 49 insertions(+)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index bdde807..954f37c 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -592,16 +592,18 @@ struct kvm_vcpu_arch {
u64 pat;
unsigned switch_db_regs;
unsigned long db[KVM_NR_DB_REGS];
unsigned long dr6;
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;
u64 mcg_ctl;
u64 mcg_ext_ctl;
u64 *mce_banks;
/* Cache MMIO info */
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index afa7bbb..0109bc0 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -862,16 +862,19 @@ void kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx, u32 *ecx, u32 *edx)
trace_kvm_cpuid(function, *eax, *ebx, *ecx, *edx);
}
EXPORT_SYMBOL_GPL(kvm_cpuid);
void kvm_emulate_cpuid(struct kvm_vcpu *vcpu)
{
u32 function, eax, ebx, ecx, edx;
+ if (cpuid_fault_enabled(vcpu) && !kvm_require_cpl(vcpu, 0))
+ return;
+
function = eax = kvm_register_read(vcpu, VCPU_REGS_RAX);
ecx = kvm_register_read(vcpu, VCPU_REGS_RCX);
kvm_cpuid(vcpu, &eax, &ebx, &ecx, &edx);
kvm_register_write(vcpu, VCPU_REGS_RAX, eax);
kvm_register_write(vcpu, VCPU_REGS_RBX, ebx);
kvm_register_write(vcpu, VCPU_REGS_RCX, ecx);
kvm_register_write(vcpu, VCPU_REGS_RDX, edx);
kvm_x86_ops->skip_emulated_instruction(vcpu);
diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
index 35058c2..a6fd40a 100644
--- a/arch/x86/kvm/cpuid.h
+++ b/arch/x86/kvm/cpuid.h
@@ -200,9 +200,20 @@ static inline int guest_cpuid_stepping(struct kvm_vcpu *vcpu)
best = kvm_find_cpuid_entry(vcpu, 0x1, 0);
if (!best)
return -1;
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
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index cbd7b92..0ddedd4 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -3793,16 +3793,23 @@ static int em_sti(struct x86_emulate_ctxt *ctxt)
ctxt->interruptibility = KVM_X86_SHADOW_INT_STI;
ctxt->eflags |= X86_EFLAGS_IF;
return X86EMUL_CONTINUE;
}
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);
ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx);
*reg_write(ctxt, VCPU_REGS_RAX) = eax;
*reg_write(ctxt, VCPU_REGS_RBX) = ebx;
*reg_write(ctxt, VCPU_REGS_RCX) = ecx;
*reg_write(ctxt, VCPU_REGS_RDX) = edx;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3017de0..62f254a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -986,16 +986,18 @@ static u32 emulated_msrs[] = {
MSR_IA32_TSC_ADJUST,
MSR_IA32_TSCDEADLINE,
MSR_IA32_MISC_ENABLE,
MSR_IA32_MCG_STATUS,
MSR_IA32_MCG_CTL,
MSR_IA32_MCG_EXT_CTL,
MSR_IA32_SMBASE,
+ MSR_PLATFORM_INFO,
+ MSR_MISC_FEATURES_ENABLES,
};
static unsigned num_emulated_msrs;
bool kvm_valid_efer(struct kvm_vcpu *vcpu, u64 efer)
{
if (efer & efer_reserved_bits)
return false;
@@ -2269,16 +2271,31 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
return 1;
vcpu->arch.osvw.length = data;
break;
case MSR_AMD64_OSVW_STATUS:
if (!guest_cpuid_has_osvw(vcpu))
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);
if (kvm_pmu_is_valid_msr(vcpu, msr))
return kvm_pmu_set_msr(vcpu, msr_info);
if (!ignore_msrs) {
vcpu_unimpl(vcpu, "unhandled wrmsr: 0x%x data 0x%llx\n",
msr, data);
@@ -2483,16 +2500,22 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
return 1;
msr_info->data = vcpu->arch.osvw.length;
break;
case MSR_AMD64_OSVW_STATUS:
if (!guest_cpuid_has_osvw(vcpu))
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);
if (!ignore_msrs) {
vcpu_unimpl(vcpu, "unhandled rdmsr: 0x%x\n", msr_info->index);
return 1;
} else {
vcpu_unimpl(vcpu, "ignored rdmsr: 0x%x\n", msr_info->index);
@@ -7508,16 +7531,19 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
kvm_clear_async_pf_completion_queue(vcpu);
kvm_async_pf_hash_reset(vcpu);
vcpu->arch.apf.halted = false;
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));
vcpu->arch.regs_avail = ~0;
vcpu->arch.regs_dirty = ~0;
kvm_x86_ops->vcpu_reset(vcpu, init_event);
}
--
2.10.2