[RFC 06/10] i386/cpu: Introduce enable_cpuid_0x1f to force exposing CPUID 0x1f

[Zhao Liu <zhao1.liu@intel.com>]

From: Xiaoyao Li <xiaoyao.li@intel.com>

Currently, QEMU exposes CPUID 0x1f to guest only when necessary, i.e.,
when topology level that cannot be enumerated by leaf 0xB, e.g., die or
module level, are configured for the guest, e.g., -smp xx,dies=2.

However, TDX architecture forces to require CPUID 0x1f to configure CPU
topology.

Introduce a bool flag, enable_cpuid_0x1f, in CPU for the case that
requires CPUID leaf 0x1f to be exposed to guest.

Introduce a new function x86_has_cpuid_0x1f(), which is the warpper of
cpu->enable_cpuid_0x1f and x86_has_extended_topo() to check if it needs
to enable cpuid leaf 0x1f for the guest.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
---
 target/i386/cpu.c     | 4 ++--
 target/i386/cpu.h     | 9 +++++++++
 target/i386/kvm/kvm.c | 2 +-
 3 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index d90e048d48f2..e0716dbe5934 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -7292,7 +7292,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
         break;
     case 0x1F:
         /* V2 Extended Topology Enumeration Leaf */
-        if (!x86_has_extended_topo(env->avail_cpu_topo)) {
+        if (!x86_has_cpuid_0x1f(cpu)) {
             *eax = *ebx = *ecx = *edx = 0;
             break;
         }
@@ -8178,7 +8178,7 @@ void x86_cpu_expand_features(X86CPU *cpu, Error **errp)
          * cpu->vendor_cpuid_only has been unset for compatibility with older
          * machine types.
          */
-        if (x86_has_extended_topo(env->avail_cpu_topo) &&
+        if (x86_has_cpuid_0x1f(cpu) &&
             (IS_INTEL_CPU(env) || !cpu->vendor_cpuid_only)) {
             x86_cpu_adjust_level(cpu, &env->cpuid_min_level, 0x1F);
         }
diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 76f24446a55d..3910b488f775 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -2251,6 +2251,9 @@ struct ArchCPU {
     /* Compatibility bits for old machine types: */
     bool enable_cpuid_0xb;
 
+    /* Force to enable cpuid 0x1f */
+    bool enable_cpuid_0x1f;
+
     /* Enable auto level-increase for all CPUID leaves */
     bool full_cpuid_auto_level;
 
@@ -2513,6 +2516,12 @@ void host_cpuid(uint32_t function, uint32_t count,
                 uint32_t *eax, uint32_t *ebx, uint32_t *ecx, uint32_t *edx);
 bool cpu_has_x2apic_feature(CPUX86State *env);
 
+static inline bool x86_has_cpuid_0x1f(X86CPU *cpu)
+{
+    return cpu->enable_cpuid_0x1f ||
+           x86_has_extended_topo(cpu->env.avail_cpu_topo);
+}
+
 /* helper.c */
 void x86_cpu_set_a20(X86CPU *cpu, int a20_state);
 void cpu_sync_avx_hflag(CPUX86State *env);
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 6c749d4ee812..23b8de308525 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -1863,7 +1863,7 @@ static uint32_t kvm_x86_build_cpuid(CPUX86State *env,
             break;
         }
         case 0x1f:
-            if (!x86_has_extended_topo(env->avail_cpu_topo)) {
+            if (!x86_has_cpuid_0x1f(env_archcpu(env))) {
                 cpuid_i--;
                 break;
             }
-- 
2.34.1