[RFC PATCH v4 03/36] target/i386: Implement mc->kvm_type() to get VM type

[Xiaoyao Li <xiaoyao.li@xxxxxxxxx>]

TDX VM requires VM type KVM_X86_TDX_VM to be passed to
kvm_ioctl(KVM_CREATE_VM). Hence implement mc->kvm_type() for i386
architecture.

If tdx-guest object is specified to confidential-guest-support, like,

  qemu -machine ...,confidential-guest-support=tdx0 \
       -object tdx-guest,id=tdx0,...

it parses VM type as KVM_X86_TDX_VM. Otherwise, it's KVM_X86_DEFAULT_VM.

Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
---
 hw/i386/x86.c              |  6 ++++++
 target/i386/kvm/kvm.c      | 30 ++++++++++++++++++++++++++++++
 target/i386/kvm/kvm_i386.h |  1 +
 3 files changed, 37 insertions(+)

diff --git a/hw/i386/x86.c b/hw/i386/x86.c
index fba790f7b49c..4d0b0047627d 100644
--- a/hw/i386/x86.c
+++ b/hw/i386/x86.c
@@ -1345,6 +1345,11 @@ static void machine_set_sgx_epc(Object *obj, Visitor *v, const char *name,
     qapi_free_SgxEPCList(list);
 }
 
+static int x86_kvm_type(MachineState *ms, const char *vm_type)
+{
+    return kvm_get_vm_type(ms, vm_type);
+}
+
 static void x86_machine_initfn(Object *obj)
 {
     X86MachineState *x86ms = X86_MACHINE(obj);
@@ -1368,6 +1373,7 @@ static void x86_machine_class_init(ObjectClass *oc, void *data)
     mc->cpu_index_to_instance_props = x86_cpu_index_to_props;
     mc->get_default_cpu_node_id = x86_get_default_cpu_node_id;
     mc->possible_cpu_arch_ids = x86_possible_cpu_arch_ids;
+    mc->kvm_type = x86_kvm_type;
     x86mc->save_tsc_khz = true;
     x86mc->fwcfg_dma_enabled = true;
     nc->nmi_monitor_handler = x86_nmi;
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index c885763a5bb5..3f8a9183fa9b 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -30,6 +30,7 @@
 #include "sysemu/runstate.h"
 #include "kvm_i386.h"
 #include "sev.h"
+#include "tdx.h"
 #include "hyperv.h"
 #include "hyperv-proto.h"
 
@@ -142,6 +143,35 @@ static struct kvm_msr_list *kvm_feature_msrs;
 #define BUS_LOCK_SLICE_TIME 1000000000ULL /* ns */
 static RateLimit bus_lock_ratelimit_ctrl;
 
+static const char* vm_type_name[] = {
+    [KVM_X86_DEFAULT_VM] = "X86_DEFAULT_VM",
+    [KVM_X86_TDX_VM] = "X86_TDX_VM",
+};
+
+int kvm_get_vm_type(MachineState *ms, const char *vm_type)
+{
+    int kvm_type = KVM_X86_DEFAULT_VM;
+
+    if (ms->cgs && object_dynamic_cast(OBJECT(ms->cgs), TYPE_TDX_GUEST)) {
+        kvm_type = KVM_X86_TDX_VM;
+    }
+
+    /*
+     * old KVM doesn't support KVM_CAP_VM_TYPES and KVM_X86_DEFAULT_VM
+     * is always supported
+     */
+    if (kvm_type == KVM_X86_DEFAULT_VM) {
+        return kvm_type;
+    }
+
+    if (!(kvm_check_extension(KVM_STATE(ms->accelerator), KVM_CAP_VM_TYPES) & BIT(kvm_type))) {
+        error_report("vm-type %s not supported by KVM", vm_type_name[kvm_type]);
+        exit(1);
+    }
+
+    return kvm_type;
+}
+
 int kvm_has_pit_state2(void)
 {
     return has_pit_state2;
diff --git a/target/i386/kvm/kvm_i386.h b/target/i386/kvm/kvm_i386.h
index 4124912c202e..b434feaa6b1d 100644
--- a/target/i386/kvm/kvm_i386.h
+++ b/target/i386/kvm/kvm_i386.h
@@ -37,6 +37,7 @@ bool kvm_has_adjust_clock(void);
 bool kvm_has_adjust_clock_stable(void);
 bool kvm_has_exception_payload(void);
 void kvm_synchronize_all_tsc(void);
+int kvm_get_vm_type(MachineState *ms, const char *vm_type);
 void kvm_arch_reset_vcpu(X86CPU *cs);
 void kvm_arch_do_init_vcpu(X86CPU *cs);
 
-- 
2.27.0