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Re: [PATCH RFC 22/22] i386: expand Hyper-V features early
From: |
Vitaly Kuznetsov |
Subject: |
Re: [PATCH RFC 22/22] i386: expand Hyper-V features early |
Date: |
Tue, 22 Sep 2020 12:33:41 +0200 |
Eduardo Habkost <ehabkost@redhat.com> writes:
> On Fri, Sep 04, 2020 at 04:54:31PM +0200, Vitaly Kuznetsov wrote:
>> To make Hyper-V features appear in e.g. QMP query-cpu-model-expansion we
>> need to expand and set the corresponding CPUID leaves early. Modify
>> x86_cpu_get_supported_feature_word() to call newly intoduced Hyper-V
>> specific kvm_hv_get_supported_cpuid() instead of
>> kvm_arch_get_supported_cpuid(). We can't use kvm_arch_get_supported_cpuid()
>> as Hyper-V specific CPUID leaves intersect with KVM's.
>>
>> Note, early expansion will only happen when KVM supports system wide
>> KVM_GET_SUPPORTED_HV_CPUID ioctl (KVM_CAP_SYS_HYPERV_CPUID).
>
> Will this implicitly enable hyperv CPUID passthrough when using
> "-cpu host"? Do we want it to?
>
I hope it won't. With 'hv_*' features set explicitly we will get just
them (if the host supports), with 'hv_passthrough' we will get
everything supported by the host. With no 'hv_*' parameters on the
command line we should get no Hyper-V features. I'll check this.
Personally, I don't think '-host' mode should enable any Hyper-V
features as these features have side-effects. E.g. if you enable SynIC
you won't be able to use vAPIC. Probably not a reasonable default for
the majority of the guests which (hopefully) are Linux.
>>
>> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
>> ---
>> target/i386/cpu.c | 15 +++++++++------
>> target/i386/kvm.c | 15 +++++++++++++++
>> target/i386/kvm_i386.h | 7 +++++++
>> 3 files changed, 31 insertions(+), 6 deletions(-)
>>
>> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
>> index 479c4bbbf459..d3c4ecb3535c 100644
>> --- a/target/i386/cpu.c
>> +++ b/target/i386/cpu.c
>> @@ -5147,7 +5147,7 @@ CpuDefinitionInfoList *qmp_query_cpu_definitions(Error
>> **errp)
>> return cpu_list;
>> }
>>
>> -static uint64_t x86_cpu_get_supported_feature_word(FeatureWord w,
>> +static uint64_t x86_cpu_get_supported_feature_word(X86CPU *cpu, FeatureWord
>> w,
>> bool migratable_only)
>> {
>> FeatureWordInfo *wi = &feature_word_info[w];
>> @@ -5156,9 +5156,12 @@ static uint64_t
>> x86_cpu_get_supported_feature_word(FeatureWord w,
>> if (kvm_enabled()) {
>> switch (wi->type) {
>> case CPUID_FEATURE_WORD:
>> - r = kvm_arch_get_supported_cpuid(kvm_state, wi->cpuid.eax,
>> - wi->cpuid.ecx,
>> - wi->cpuid.reg);
>> + if (hyperv_feature_word(w))
>> + r = kvm_hv_get_supported_cpuid(cpu, w);
>> + else
>> + r = kvm_arch_get_supported_cpuid(kvm_state, wi->cpuid.eax,
>> + wi->cpuid.ecx,
>> + wi->cpuid.reg);
>> break;
>> case MSR_FEATURE_WORD:
>> r = kvm_arch_get_supported_msr_feature(kvm_state,
>> @@ -6485,7 +6488,7 @@ static void x86_cpu_expand_features(X86CPU *cpu, Error
>> **errp)
>> * by the user.
>> */
>> env->features[w] |=
>> - x86_cpu_get_supported_feature_word(w, cpu->migratable) &
>> + x86_cpu_get_supported_feature_word(cpu, w, cpu->migratable)
>> &
>> ~env->user_features[w] &
>> ~feature_word_info[w].no_autoenable_flags;
>> }
>> @@ -6589,7 +6592,7 @@ static void x86_cpu_filter_features(X86CPU *cpu, bool
>> verbose)
>>
>> for (w = 0; w < FEATURE_WORDS; w++) {
>> uint64_t host_feat =
>> - x86_cpu_get_supported_feature_word(w, false);
>> + x86_cpu_get_supported_feature_word(cpu, w, false);
>> uint64_t requested_features = env->features[w];
>> uint64_t unavailable_features = requested_features & ~host_feat;
>> mark_unavailable_features(cpu, w, unavailable_features, prefix);
>> diff --git a/target/i386/kvm.c b/target/i386/kvm.c
>> index 961241528a5c..764b96fbbb7d 100644
>> --- a/target/i386/kvm.c
>> +++ b/target/i386/kvm.c
>> @@ -1449,6 +1449,21 @@ static int hyperv_fill_cpuids(CPUState *cs,
>> return cpuid_i;
>> }
>>
>> +uint32_t kvm_hv_get_supported_cpuid(X86CPU *cpu, enum FeatureWord w)
>> +{
>> + CPUState *cs = CPU(cpu);
>> + CPUX86State *env = &cpu->env;
>> + Error *local_err = NULL;
>> +
>> + hyperv_expand_features(cs, &local_err);
>> +
>> + if (local_err) {
>> + error_report_err(local_err);
>> + }
>> +
>> + return env->features[w];
>> +}
>> +
>> static Error *hv_passthrough_mig_blocker;
>> static Error *hv_no_nonarch_cs_mig_blocker;
>>
>> diff --git a/target/i386/kvm_i386.h b/target/i386/kvm_i386.h
>> index 064b8798a26c..2e7da4f39668 100644
>> --- a/target/i386/kvm_i386.h
>> +++ b/target/i386/kvm_i386.h
>> @@ -48,4 +48,11 @@ bool kvm_has_waitpkg(void);
>>
>> bool kvm_hv_vpindex_settable(void);
>>
>> +static inline bool hyperv_feature_word(enum FeatureWord w)
>> +{
>> + return w >= FEAT_HYPERV_EAX && w <= FEAT_HV_NESTED_EDX;
>> +}
>> +
>> +uint32_t kvm_hv_get_supported_cpuid(X86CPU *cpu, enum FeatureWord w);
>> +
>> #endif
>> --
>> 2.25.4
>>
--
Vitaly
- Re: [PATCH RFC 09/22] i386: add reserved FEAT_HYPERV_ECX CPUID leaf, (continued)
- [PATCH RFC 13/22] i386: split hyperv_handle_properties() into hyperv_expand_features()/hyperv_fill_cpuids(), Vitaly Kuznetsov, 2020/09/04
- [PATCH RFC 12/22] i386: always fill Hyper-V CPUID feature leaves from X86CPU data, Vitaly Kuznetsov, 2020/09/04
- [PATCH RFC 15/22] i386: switch hyperv_expand_features() to using error_setg(), Vitaly Kuznetsov, 2020/09/04
- [PATCH RFC 18/22] i386: prefer system KVM_GET_SUPPORTED_HV_CPUID ioctl over vCPU's one, Vitaly Kuznetsov, 2020/09/04
- [PATCH RFC 22/22] i386: expand Hyper-V features early, Vitaly Kuznetsov, 2020/09/04
- [PATCH RFC 21/22] i386: record if Hyper-V features were already expanded, Vitaly Kuznetsov, 2020/09/04
- [PATCH RFC 19/22] i386: prepare hyperv_expand_features() to be called at CPU feature expansion time, Vitaly Kuznetsov, 2020/09/04
- [PATCH RFC 16/22] i386: make hyperv_expand_features() return void, Vitaly Kuznetsov, 2020/09/04
- [PATCH RFC 17/22] i386: adjust the expected KVM_GET_SUPPORTED_HV_CPUID array size, Vitaly Kuznetsov, 2020/09/04
- [PATCH RFC 20/22] i386: use global kvm_state in hyperv_enabled() check, Vitaly Kuznetsov, 2020/09/04