[PATCH RFC 22/22] i386: expand Hyper-V features early

[Vitaly Kuznetsov]

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).

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