[PATCH v3 18/19] i386: provide simple 'hv-default=on' option

[Vitaly Kuznetsov <vkuznets@redhat.com>]

Enabling Hyper-V emulation for a Windows VM is a tiring experience as it
requires listing all currently supported enlightenments ("hv-*" CPU
features) explicitly. We do have 'hv-passthrough' mode enabling
everything but it can't be used in production as it prevents migration.

Introduce a simple 'hv-default=on' CPU flag enabling all currently supported
Hyper-V enlightenments. Later, when new enlightenments get implemented,
compat_props mechanism will be used to disable them for legacy machine types,
this will keep 'hv-default=on' configurations migratable.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 docs/hyperv.txt   | 16 +++++++++++++---
 target/i386/cpu.c | 38 ++++++++++++++++++++++++++++++++++++++
 target/i386/cpu.h |  5 +++++
 3 files changed, 56 insertions(+), 3 deletions(-)

diff --git a/docs/hyperv.txt b/docs/hyperv.txt
index 5df00da54fc4..a54c066cab09 100644
--- a/docs/hyperv.txt
+++ b/docs/hyperv.txt
@@ -17,10 +17,20 @@ compatible hypervisor and use Hyper-V specific features.
 
 2. Setup
 =========
-No Hyper-V enlightenments are enabled by default by either KVM or QEMU. In
-QEMU, individual enlightenments can be enabled through CPU flags, e.g:
+All currently supported Hyper-V enlightenments can be enabled by specifying
+'hv-default=on' CPU flag:
 
-  qemu-system-x86_64 --enable-kvm --cpu host,hv_relaxed,hv_vpindex,hv_time, ...
+  qemu-system-x86_64 --enable-kvm --cpu host,hv-default ...
+
+Alternatively, it is possible to do fine-grained enablement through CPU flags,
+e.g:
+
+  qemu-system-x86_64 --enable-kvm --cpu host,hv-relaxed,hv-vpindex,hv-time ...
+
+It is also possible to disable individual enlightenments from the default list,
+this can be used for debugging purposes:
+
+  qemu-system-x86_64 --enable-kvm --cpu host,hv-default=on,hv-evmcs=off ...
 
 Sometimes there are dependencies between enlightenments, QEMU is supposed to
 check that the supplied configuration is sane.
diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 48007a876e32..99338de00f78 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -4552,6 +4552,24 @@ static void x86_cpuid_set_tsc_freq(Object *obj, Visitor *v, const char *name,
     cpu->env.tsc_khz = cpu->env.user_tsc_khz = value / 1000;
 }
 
+static bool x86_hv_default_get(Object *obj, Error **errp)
+{
+    X86CPU *cpu = X86_CPU(obj);
+
+    return cpu->hyperv_default;
+}
+
+static void x86_hv_default_set(Object *obj, bool value, Error **errp)
+{
+    X86CPU *cpu = X86_CPU(obj);
+
+    cpu->hyperv_default = value;
+
+    if (value) {
+        cpu->hyperv_features |= cpu->hyperv_default_features;
+    }
+}
+
 /* Generic getter for "feature-words" and "filtered-features" properties */
 static void x86_cpu_get_feature_words(Object *obj, Visitor *v,
                                       const char *name, void *opaque,
@@ -6955,10 +6973,26 @@ static void x86_cpu_initfn(Object *obj)
     object_property_add_alias(obj, "pause_filter", obj, "pause-filter");
     object_property_add_alias(obj, "sse4_1", obj, "sse4.1");
     object_property_add_alias(obj, "sse4_2", obj, "sse4.2");
+    object_property_add_alias(obj, "hv_default", obj, "hv-default");
 
     if (xcc->model) {
         x86_cpu_load_model(cpu, xcc->model);
     }
+
+    /* Hyper-V features enabled with 'hv-default=on' */
+    cpu->hyperv_default_features = BIT(HYPERV_FEAT_RELAXED) |
+        BIT(HYPERV_FEAT_VAPIC) | BIT(HYPERV_FEAT_TIME) |
+        BIT(HYPERV_FEAT_CRASH) | BIT(HYPERV_FEAT_RESET) |
+        BIT(HYPERV_FEAT_VPINDEX) | BIT(HYPERV_FEAT_RUNTIME) |
+        BIT(HYPERV_FEAT_SYNIC) | BIT(HYPERV_FEAT_STIMER) |
+        BIT(HYPERV_FEAT_FREQUENCIES) | BIT(HYPERV_FEAT_REENLIGHTENMENT) |
+        BIT(HYPERV_FEAT_TLBFLUSH) | BIT(HYPERV_FEAT_IPI) |
+        BIT(HYPERV_FEAT_STIMER_DIRECT);
+
+    /* Enlightened VMCS is only available on Intel/VMX */
+    if (kvm_hv_evmcs_available()) {
+        cpu->hyperv_default_features |= BIT(HYPERV_FEAT_EVMCS);
+    }
 }
 
 static int64_t x86_cpu_get_arch_id(CPUState *cs)
@@ -7285,6 +7319,10 @@ static void x86_cpu_common_class_init(ObjectClass *oc, void *data)
                               x86_cpu_get_crash_info_qom, NULL, NULL, NULL);
 #endif
 
+    object_class_property_add_bool(oc, "hv-default",
+                              x86_hv_default_get,
+                              x86_hv_default_set);
+
     for (w = 0; w < FEATURE_WORDS; w++) {
         int bitnr;
         for (bitnr = 0; bitnr < 64; bitnr++) {
diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 6220cb2cabb9..8a484becb6b9 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -1657,6 +1657,11 @@ struct X86CPU {
     bool hyperv_synic_kvm_only;
     uint64_t hyperv_features;
     bool hyperv_passthrough;
+
+    /* 'hv-default' enablement */
+    uint64_t hyperv_default_features;
+    bool hyperv_default;
+
     OnOffAuto hyperv_no_nonarch_cs;
     uint32_t hyperv_vendor_id[3];
     uint32_t hyperv_interface_id[4];
-- 
2.29.2