[PATCH 1/2] Add HvExtCallQueryCapabilities

[Florian Schmidt <flosch@nutanix.com>]

On CPUID leaf 0x40000003, EBX bit 20 signals that we support
the HvExtCallQueryCapabilities hypercall. This returns a bit field which
signals which further extended hypercalls are supported (as a way to
conserve CPUID leaf bits).

We'll track such capabilities in kvm_hyperv_properties like all the
others, but they will have a ".reg" entry of 0, since they aren't
returned via CPUID and so don't have a corresponding register.

For now, we don't support any extended hypercalls, but we'll add
HvExtCallGetBootZeroedMemory in a followup patch.

Signed-off-by: Florian Schmidt <flosch@nutanix.com>
---
 docs/system/i386/hyperv.rst      |  7 +++++++
 hw/hyperv/hyperv.c               | 28 ++++++++++++++++++++++++++++
 include/hw/hyperv/hyperv-proto.h |  1 +
 include/hw/hyperv/hyperv.h       |  5 +++++
 target/i386/cpu.c                |  2 ++
 target/i386/cpu.h                |  1 +
 target/i386/kvm/hyperv-proto.h   |  1 +
 target/i386/kvm/hyperv.c         |  6 ++++++
 target/i386/kvm/kvm.c            | 12 ++++++++++++
 target/i386/kvm/kvm_i386.h       |  2 ++
 10 files changed, 65 insertions(+)

diff --git a/docs/system/i386/hyperv.rst b/docs/system/i386/hyperv.rst
index e1babffb0f..a1985dc418 100644
--- a/docs/system/i386/hyperv.rst
+++ b/docs/system/i386/hyperv.rst
@@ -259,6 +259,13 @@ Existing enlightenments
 
   Recommended: ``hv-evmcs`` (Intel)
 
+``hv-ext-query-caps``
+  Certain "extended hypercalls" are not signaled to the guest directly via
+  CPUID bits, but use a separate hypercall that returns a bitfield to signal
+  support for them. This enables this hypercall. On its own, it does not
+  provide any useful new functionality, but it's required to be enabled to use
+  any extended hypercalls.
+
 Supplementary features
 ----------------------
 
diff --git a/hw/hyperv/hyperv.c b/hw/hyperv/hyperv.c
index 900ff80213..3dcf23ba53 100644
--- a/hw/hyperv/hyperv.c
+++ b/hw/hyperv/hyperv.c
@@ -702,6 +702,34 @@ int hyperv_set_event_flag_handler(uint32_t conn_id, EventNotifier *notifier)
     return set_event_flag_handler(conn_id, notifier);
 }
 
+uint16_t hyperv_ext_hcall_query_caps(uint64_t sup, uint64_t outgpa, bool fast)
+{
+    uint16_t ret;
+    uint64_t *supported = NULL;
+    hwaddr len;
+
+    if (fast) {
+        ret = HV_STATUS_INVALID_HYPERCALL_CODE;
+        goto cleanup;
+    }
+
+    len = sizeof(*supported);
+    supported = cpu_physical_memory_map(outgpa, &len, 1);
+    if (!supported || len < sizeof(*supported)) {
+        ret = HV_STATUS_INSUFFICIENT_MEMORY;
+        goto cleanup;
+    }
+
+    *supported = sup;
+    ret = HV_STATUS_SUCCESS;
+
+cleanup:
+    if (supported) {
+        cpu_physical_memory_unmap(supported, sizeof(*supported), 1, len);
+    }
+    return ret;
+}
+
 uint16_t hyperv_hcall_signal_event(uint64_t param, bool fast)
 {
     EventFlagHandler *handler;
diff --git a/include/hw/hyperv/hyperv-proto.h b/include/hw/hyperv/hyperv-proto.h
index fffc5ce342..f1d1d2eb26 100644
--- a/include/hw/hyperv/hyperv-proto.h
+++ b/include/hw/hyperv/hyperv-proto.h
@@ -35,6 +35,7 @@
 #define HV_POST_DEBUG_DATA                    0x0069
 #define HV_RETRIEVE_DEBUG_DATA                0x006a
 #define HV_RESET_DEBUG_SESSION                0x006b
+#define HV_EXT_CALL_QUERY_CAPABILITIES        0x8001
 #define HV_HYPERCALL_FAST                     (1u << 16)
 
 /*
diff --git a/include/hw/hyperv/hyperv.h b/include/hw/hyperv/hyperv.h
index 23091301d0..e29d60f565 100644
--- a/include/hw/hyperv/hyperv.h
+++ b/include/hw/hyperv/hyperv.h
@@ -97,6 +97,11 @@ uint16_t hyperv_hcall_retreive_dbg_data(uint64_t ingpa, uint64_t outgpa,
  */
 uint16_t hyperv_hcall_post_dbg_data(uint64_t ingpa, uint64_t outgpa, bool fast);
 
+/*
+ * Process HVCALL_EXT_QUERY_CAPABILITIES hypercall.
+ */
+uint16_t hyperv_ext_hcall_query_caps(uint64_t sup, uint64_t outgpa, bool fast);
+
 uint32_t hyperv_syndbg_send(uint64_t ingpa, uint32_t count);
 uint32_t hyperv_syndbg_recv(uint64_t ingpa, uint32_t count);
 void hyperv_syndbg_set_pending_page(uint64_t ingpa);
diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 5805d33ab9..ed9773ac9e 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -10768,6 +10768,8 @@ static const Property x86_cpu_properties[] = {
                       HYPERV_FEAT_TLBFLUSH_EXT, 0),
     DEFINE_PROP_BIT64("hv-tlbflush-direct", X86CPU, hyperv_features,
                       HYPERV_FEAT_TLBFLUSH_DIRECT, 0),
+    DEFINE_PROP_BIT64("hv-ext-query-caps", X86CPU, hyperv_features,
+                      HYPERV_FEAT_EXT_CALLS, 0),
     DEFINE_PROP_ON_OFF_AUTO("hv-no-nonarch-coresharing", X86CPU,
                             hyperv_no_nonarch_cs, ON_OFF_AUTO_OFF),
 #ifdef CONFIG_SYNDBG
diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index e6a197602d..6737340766 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -1480,6 +1480,7 @@ uint64_t x86_cpu_get_supported_feature_word(X86CPU *cpu, FeatureWord w);
 #define HYPERV_FEAT_XMM_INPUT           18
 #define HYPERV_FEAT_TLBFLUSH_EXT        19
 #define HYPERV_FEAT_TLBFLUSH_DIRECT     20
+#define HYPERV_FEAT_EXT_CALLS           21
 
 #ifndef HYPERV_SPINLOCK_NEVER_NOTIFY
 #define HYPERV_SPINLOCK_NEVER_NOTIFY             0xFFFFFFFF
diff --git a/target/i386/kvm/hyperv-proto.h b/target/i386/kvm/hyperv-proto.h
index a9f056f2f3..4eb2955ac5 100644
--- a/target/i386/kvm/hyperv-proto.h
+++ b/target/i386/kvm/hyperv-proto.h
@@ -46,6 +46,7 @@
  */
 #define HV_POST_MESSAGES             (1u << 4)
 #define HV_SIGNAL_EVENTS             (1u << 5)
+#define HV_ENABLE_EXT_HYPERCALLS     (1u << 20)
 
 /*
  * HV_CPUID_FEATURES.EDX bits
diff --git a/target/i386/kvm/hyperv.c b/target/i386/kvm/hyperv.c
index 420c76b5ff..807acaf6b1 100644
--- a/target/i386/kvm/hyperv.c
+++ b/target/i386/kvm/hyperv.c
@@ -17,6 +17,7 @@
 #include "hyperv.h"
 #include "hw/hyperv/hyperv.h"
 #include "hyperv-proto.h"
+#include "kvm_i386.h"
 
 int hyperv_x86_synic_add(X86CPU *cpu)
 {
@@ -117,6 +118,11 @@ int kvm_hv_handle_exit(X86CPU *cpu, struct kvm_hyperv_exit *exit)
             exit->u.hcall.result =
                 hyperv_hcall_reset_dbg_session(out_param);
             break;
+        case HV_EXT_CALL_QUERY_CAPABILITIES:
+            exit->u.hcall.result =
+                hyperv_ext_hcall_query_caps(hv_build_ext_call_caps(CPU(cpu)),
+                                            out_param, fast);
+            break;
         default:
             exit->u.hcall.result = HV_STATUS_INVALID_HYPERCALL_CODE;
         }
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 4272b6770c..bc1e44c33e 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -1137,6 +1137,13 @@ static struct {
         },
         .dependencies = BIT(HYPERV_FEAT_VAPIC)
     },
+    [HYPERV_FEAT_EXT_CALLS] = {
+        .desc = "query availability of extended hypercalls (hv-ext-query-caps)",
+        .flags = {
+            {.func = HV_CPUID_FEATURES, .reg = R_EBX,
+             .bits = HV_ENABLE_EXT_HYPERCALLS}
+        }
+    },
 };
 
 static struct kvm_cpuid2 *try_get_hv_cpuid(CPUState *cs, int max,
@@ -1434,6 +1441,11 @@ static uint32_t hv_build_cpuid_leaf(CPUState *cs, uint32_t func, int reg)
     return r;
 }
 
+uint64_t hv_build_ext_call_caps(CPUState *cs)
+{
+    return hv_build_cpuid_leaf(cs, HV_EXT_CALL_QUERY_CAPABILITIES, 0);
+}
+
 /*
  * Expand Hyper-V CPU features. In partucular, check that all the requested
  * features are supported by the host and the sanity of the configuration
diff --git a/target/i386/kvm/kvm_i386.h b/target/i386/kvm/kvm_i386.h
index 2b653442f4..8c71ad01af 100644
--- a/target/i386/kvm/kvm_i386.h
+++ b/target/i386/kvm/kvm_i386.h
@@ -72,6 +72,8 @@ struct kvm_cpuid_entry2 *cpuid_find_entry(struct kvm_cpuid2 *cpuid,
 uint32_t cpuid_entry_get_reg(struct kvm_cpuid_entry2 *entry, int reg);
 uint32_t kvm_x86_build_cpuid(CPUX86State *env, struct kvm_cpuid_entry2 *entries,
                              uint32_t cpuid_i);
+
+uint64_t hv_build_ext_call_caps(CPUState *cs);
 #endif /* CONFIG_KVM */
 
 void kvm_smm_cpu_address_space_init(X86CPU *cpu);
-- 
2.47.3