| Message ID | 20161101013749.4003-8-khuey@kylehuey.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
> + vcpu->arch.cpuid_fault = false; This should be conditional on "if (!init_event)". Most MSRs are untouched on an INIT IPI. Otherwise looks good. The patch is independent of the rest, so I would prefer to take it through the KVM tree. Thanks, Paolo > kvm_make_request(KVM_REQ_EVENT, vcpu); > vcpu->arch.apf.msr_val = 0; > vcpu->arch.st.msr_val = 0; > > kvmclock_reset(vcpu); > > kvm_clear_async_pf_completion_queue(vcpu); > kvm_async_pf_hash_reset(vcpu); > -- > 2.10.2 > > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, 1 Nov 2016, Paolo Bonzini wrote: > > > + vcpu->arch.cpuid_fault = false; > > This should be conditional on "if (!init_event)". Most MSRs are untouched > on an INIT IPI. > > Otherwise looks good. The patch is independent of the rest, so I would > prefer to take it through the KVM tree. > It depends on the FEATURE_ENABLES MSR define, which is part of that series. Thanks tglx -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, Oct 31, 2016 at 6:37 PM, Kyle Huey <me@kylehuey.com> wrote: > 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> > --- > arch/x86/include/asm/kvm_host.h | 1 + > arch/x86/kvm/cpuid.c | 3 +++ > arch/x86/kvm/x86.c | 16 ++++++++++++++++ > 3 files changed, 20 insertions(+) > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index 4b20f73..4a6e62b 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -592,16 +592,17 @@ 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; > + bool cpuid_fault; > > 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..ed8436a 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 (vcpu->arch.cpuid_fault && !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/x86.c b/arch/x86/kvm/x86.c > index e375235..470c553 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -2269,16 +2269,21 @@ 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_MISC_FEATURES_ENABLES: > + if (data & ~CPUID_FAULT_ENABLE) > + return 1; (Due to my comments below, PLATINFO_CPUID_FAULT will not necessarily be enabled for guests. So this code will need to check if the virtual CPU supports PLATINFO_CPUID_FAULT before enabling CPUID faulting.) > + vcpu->arch.cpuid_fault = !!(data & CPUID_FAULT_ENABLE); > + 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 %llx\n", > msr, data); > @@ -2483,16 +2488,25 @@ 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: > + /* cpuid faulting is supported */ > + msr_info->data = PLATINFO_CPUID_FAULT; > + break; This could break save/restore, if for example, a VM is migrated to a version of KVM without MSR_PLATFORM_INFO support. I think the way to handle this is to make MSR_PLATFORM_INFO writeable (but only from userspace) so that hypervisors can defend themselves (by setting this MSR to 0). > + case MSR_MISC_FEATURES_ENABLES: > + msr_info->data = 0; > + if (vcpu->arch.cpuid_fault) > + msr_info->data |= CPUID_FAULT_ENABLE; > + break; MSR_MISC_FEATURES_ENABLES should be added to emulated_msrs[] so that the hypervisor will maintain the value of CPUID_FAULT_ENABLE across a save/restore. > 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); > @@ -7493,16 +7507,18 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) > kvm_update_dr0123(vcpu); > vcpu->arch.dr6 = DR6_INIT; > kvm_update_dr6(vcpu); > vcpu->arch.dr7 = DR7_FIXED_1; > kvm_update_dr7(vcpu); > > vcpu->arch.cr2 = 0; > > + vcpu->arch.cpuid_fault = false; > + > kvm_make_request(KVM_REQ_EVENT, vcpu); > vcpu->arch.apf.msr_val = 0; > vcpu->arch.st.msr_val = 0; > > kvmclock_reset(vcpu); > > kvm_clear_async_pf_completion_queue(vcpu); > kvm_async_pf_hash_reset(vcpu); > -- > 2.10.2 > > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 4b20f73..4a6e62b 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -592,16 +592,17 @@ 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; + bool cpuid_fault; 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..ed8436a 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 (vcpu->arch.cpuid_fault && !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/x86.c b/arch/x86/kvm/x86.c index e375235..470c553 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2269,16 +2269,21 @@ 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_MISC_FEATURES_ENABLES: + if (data & ~CPUID_FAULT_ENABLE) + return 1; + vcpu->arch.cpuid_fault = !!(data & CPUID_FAULT_ENABLE); + 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 %llx\n", msr, data); @@ -2483,16 +2488,25 @@ 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: + /* cpuid faulting is supported */ + msr_info->data = PLATINFO_CPUID_FAULT; + break; + case MSR_MISC_FEATURES_ENABLES: + msr_info->data = 0; + if (vcpu->arch.cpuid_fault) + msr_info->data |= CPUID_FAULT_ENABLE; + 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); @@ -7493,16 +7507,18 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) kvm_update_dr0123(vcpu); vcpu->arch.dr6 = DR6_INIT; kvm_update_dr6(vcpu); vcpu->arch.dr7 = DR7_FIXED_1; kvm_update_dr7(vcpu); vcpu->arch.cr2 = 0; + vcpu->arch.cpuid_fault = false; + kvm_make_request(KVM_REQ_EVENT, vcpu); vcpu->arch.apf.msr_val = 0; vcpu->arch.st.msr_val = 0; kvmclock_reset(vcpu); kvm_clear_async_pf_completion_queue(vcpu); kvm_async_pf_hash_reset(vcpu);
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> --- arch/x86/include/asm/kvm_host.h | 1 + arch/x86/kvm/cpuid.c | 3 +++ arch/x86/kvm/x86.c | 16 ++++++++++++++++ 3 files changed, 20 insertions(+)