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SubjectRe: [PATCH v2 5/6] kvm: x86: Emulate MSR IA32_CORE_CAPABILITIES
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On 2/4/2020 5:43 AM, Sean Christopherson wrote:
> On Mon, Feb 03, 2020 at 11:16:07PM +0800, Xiaoyao Li wrote:
>> Emulate MSR_IA32_CORE_CAPABILITIES in software and unconditionally
>> advertise its support to userspace. Like MSR_IA32_ARCH_CAPABILITIES, it
>> is a feature-enumerating MSR and can be fully emulated regardless of
>> hardware support. Existence of CORE_CAPABILITIES is enumerated via
>> CPUID.(EAX=7H,ECX=0):EDX[30].
>>
>> Note, support for individual features enumerated via CORE_CAPABILITIES,
>> e.g., split lock detection, will be added in future patches.
>>
>> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
>> ---
>> arch/x86/include/asm/kvm_host.h | 1 +
>> arch/x86/kvm/cpuid.c | 5 +++--
>> arch/x86/kvm/x86.c | 22 ++++++++++++++++++++++
>> 3 files changed, 26 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
>> index 329d01c689b7..dc231240102f 100644
>> --- a/arch/x86/include/asm/kvm_host.h
>> +++ b/arch/x86/include/asm/kvm_host.h
>> @@ -591,6 +591,7 @@ struct kvm_vcpu_arch {
>> u64 ia32_xss;
>> u64 microcode_version;
>> u64 arch_capabilities;
>> + u64 core_capabilities;
>>
>> /*
>> * Paging state of the vcpu
>> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
>> index b1c469446b07..7282d04f3a6b 100644
>> --- a/arch/x86/kvm/cpuid.c
>> +++ b/arch/x86/kvm/cpuid.c
>> @@ -409,10 +409,11 @@ static inline void do_cpuid_7_mask(struct kvm_cpuid_entry2 *entry, int index)
>> boot_cpu_has(X86_FEATURE_AMD_SSBD))
>> entry->edx |= F(SPEC_CTRL_SSBD);
>> /*
>> - * We emulate ARCH_CAPABILITIES in software even
>> - * if the host doesn't support it.
>> + * ARCH_CAPABILITIES and CORE_CAPABILITIES are emulated in
>> + * software regardless of host support.
>> */
>> entry->edx |= F(ARCH_CAPABILITIES);
>> + entry->edx |= F(CORE_CAPABILITIES);
>> break;
>> case 1:
>> entry->eax &= kvm_cpuid_7_1_eax_x86_features;
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index 821b7404c0fd..a97a8f5dd1df 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -1222,6 +1222,7 @@ static const u32 emulated_msrs_all[] = {
>> MSR_IA32_TSC_ADJUST,
>> MSR_IA32_TSCDEADLINE,
>> MSR_IA32_ARCH_CAPABILITIES,
>> + MSR_IA32_CORE_CAPS,
>> MSR_IA32_MISC_ENABLE,
>> MSR_IA32_MCG_STATUS,
>> MSR_IA32_MCG_CTL,
>> @@ -1288,6 +1289,7 @@ static const u32 msr_based_features_all[] = {
>> MSR_F10H_DECFG,
>> MSR_IA32_UCODE_REV,
>> MSR_IA32_ARCH_CAPABILITIES,
>> + MSR_IA32_CORE_CAPS,
>> };
>>
>> static u32 msr_based_features[ARRAY_SIZE(msr_based_features_all)];
>> @@ -1341,12 +1343,20 @@ static u64 kvm_get_arch_capabilities(void)
>> return data;
>> }
>>
>> +static u64 kvm_get_core_capabilities(void)
>> +{
>> + return 0;
>> +}
>> +
>> static int kvm_get_msr_feature(struct kvm_msr_entry *msr)
>> {
>> switch (msr->index) {
>> case MSR_IA32_ARCH_CAPABILITIES:
>> msr->data = kvm_get_arch_capabilities();
>> break;
>> + case MSR_IA32_CORE_CAPS:
>> + msr->data = kvm_get_core_capabilities();
>> + break;
>> case MSR_IA32_UCODE_REV:
>> rdmsrl_safe(msr->index, &msr->data);
>> break;
>> @@ -2716,6 +2726,11 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>> return 1;
>> vcpu->arch.arch_capabilities = data;
>> break;
>> + case MSR_IA32_CORE_CAPS:
>> + if (!msr_info->host_initiated)
>
> Shouldn't @data be checked against kvm_get_core_capabilities()?

Maybe it's for the case that userspace might have the ability to emulate
SLD feature? And we usually let userspace set whatever it wants, e.g.,
ARCH_CAPABILITIES.

Anyway, I have no objection to add this check.

>> + return 1;
>> + vcpu->arch.core_capabilities = data;
>> + break;
>> case MSR_EFER:
>> return set_efer(vcpu, msr_info);
>> case MSR_K7_HWCR:
>> @@ -3044,6 +3059,12 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>> return 1;
>> msr_info->data = vcpu->arch.arch_capabilities;
>> break;
>> + case MSR_IA32_CORE_CAPS:
>> + if (!msr_info->host_initiated &&
>> + !guest_cpuid_has(vcpu, X86_FEATURE_CORE_CAPABILITIES))
>> + return 1;
>> + msr_info->data = vcpu->arch.core_capabilities;
>> + break;
>> case MSR_IA32_POWER_CTL:
>> msr_info->data = vcpu->arch.msr_ia32_power_ctl;
>> break;
>> @@ -9288,6 +9309,7 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
>> goto free_guest_fpu;
>>
>> vcpu->arch.arch_capabilities = kvm_get_arch_capabilities();
>> + vcpu->arch.core_capabilities = kvm_get_core_capabilities();
>> vcpu->arch.msr_platform_info = MSR_PLATFORM_INFO_CPUID_FAULT;
>> kvm_vcpu_mtrr_init(vcpu);
>> vcpu_load(vcpu);
>> --
>> 2.23.0
>>

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