[PATCH v8 6/9] i386: kill off hv_cpuid_check_and_set()

[Vitaly Kuznetsov <vkuznets@redhat.com>]

hv_cpuid_check_and_set() does too much:
- Checks if the feature is supported by KVM;
- Checks if all dependencies are enabled;
- Sets the feature bit in cpu->hyperv_features for 'passthrough' mode.

To reduce the complexity, move all the logic except for dependencies
check out of it. Also, in 'passthrough' mode we don't really need to
check dependencies because KVM is supposed to provide a consistent
set anyway.

Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 target/i386/kvm/kvm.c | 104 +++++++++++++++---------------------------
 1 file changed, 36 insertions(+), 68 deletions(-)

diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index b679dfdfc655..1cce0969067e 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -1145,16 +1145,12 @@ static bool hyperv_feature_supported(CPUState *cs, int feature)
     return true;
 }
 
-static int hv_cpuid_check_and_set(CPUState *cs, int feature, Error **errp)
+/* Checks that all feature dependencies are enabled */
+static bool hv_feature_check_deps(X86CPU *cpu, int feature, Error **errp)
 {
-    X86CPU *cpu = X86_CPU(cs);
     uint64_t deps;
     int dep_feat;
 
-    if (!hyperv_feat_enabled(cpu, feature) && !cpu->hyperv_passthrough) {
-        return 0;
-    }
-
     deps = kvm_hyperv_properties[feature].dependencies;
     while (deps) {
         dep_feat = ctz64(deps);
@@ -1162,26 +1158,12 @@ static int hv_cpuid_check_and_set(CPUState *cs, int feature, Error **errp)
             error_setg(errp, "Hyper-V %s requires Hyper-V %s",
                        kvm_hyperv_properties[feature].desc,
                        kvm_hyperv_properties[dep_feat].desc);
-            return 1;
+            return false;
         }
         deps &= ~(1ull << dep_feat);
     }
 
-    if (!hyperv_feature_supported(cs, feature)) {
-        if (hyperv_feat_enabled(cpu, feature)) {
-            error_setg(errp, "Hyper-V %s is not supported by kernel",
-                       kvm_hyperv_properties[feature].desc);
-            return 1;
-        } else {
-            return 0;
-        }
-    }
-
-    if (cpu->hyperv_passthrough) {
-        cpu->hyperv_features |= BIT(feature);
-    }
-
-    return 0;
+    return true;
 }
 
 static uint32_t hv_build_cpuid_leaf(CPUState *cs, uint32_t func, int reg)
@@ -1220,6 +1202,8 @@ static uint32_t hv_build_cpuid_leaf(CPUState *cs, uint32_t func, int reg)
 bool kvm_hyperv_expand_features(X86CPU *cpu, Error **errp)
 {
     CPUState *cs = CPU(cpu);
+    Error *local_err = NULL;
+    int feat;
 
     if (!hyperv_enabled(cpu))
         return true;
@@ -1275,53 +1259,37 @@ bool kvm_hyperv_expand_features(X86CPU *cpu, Error **errp)
 
         cpu->hyperv_spinlock_attempts =
             hv_cpuid_get_host(cs, HV_CPUID_ENLIGHTMENT_INFO, R_EBX);
-    }
 
-    /* Features */
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_RELAXED, errp)) {
-        return false;
-    }
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_VAPIC, errp)) {
-        return false;
-    }
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_TIME, errp)) {
-        return false;
-    }
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_CRASH, errp)) {
-        return false;
-    }
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_RESET, errp)) {
-        return false;
-    }
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_VPINDEX, errp)) {
-        return false;
-    }
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_RUNTIME, errp)) {
-        return false;
-    }
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_SYNIC, errp)) {
-        return false;
-    }
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_STIMER, errp)) {
-        return false;
-    }
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_FREQUENCIES, errp)) {
-        return false;
-    }
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_REENLIGHTENMENT, errp)) {
-        return false;
-    }
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_TLBFLUSH, errp)) {
-        return false;
-    }
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_EVMCS, errp)) {
-        return false;
-    }
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_IPI, errp)) {
-        return false;
-    }
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_STIMER_DIRECT, errp)) {
-        return false;
+        /*
+         * Mark feature as enabled in 'cpu->hyperv_features' as
+         * hv_build_cpuid_leaf() uses this info to build guest CPUIDs.
+         */
+        for (feat = 0; feat < ARRAY_SIZE(kvm_hyperv_properties); feat++) {
+            if (hyperv_feature_supported(cs, feat)) {
+                cpu->hyperv_features |= BIT(feat);
+            }
+        }
+    } else {
+        /* Check features availability and dependencies */
+        for (feat = 0; feat < ARRAY_SIZE(kvm_hyperv_properties); feat++) {
+            /* If the feature was not requested skip it. */
+            if (!hyperv_feat_enabled(cpu, feat)) {
+                continue;
+            }
+
+            /* Check if the feature is supported by KVM */
+            if (!hyperv_feature_supported(cs, feat)) {
+                error_setg(errp, "Hyper-V %s is not supported by kernel",
+                           kvm_hyperv_properties[feat].desc);
+                return false;
+            }
+
+            /* Check dependencies */
+            if (!hv_feature_check_deps(cpu, feat, &local_err)) {
+                error_propagate(errp, local_err);
+                return false;
+            }
+        }
     }
 
     /* Additional dependencies not covered by kvm_hyperv_properties[] */
-- 
2.31.1