qemu-kvm/kvm-i386-cpu-Introduce-enable_cpuid_0x1f-to-force-exposi.patch

From c45bc21b4c191ceb2523bfeac4ff2eb042469d89 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Fri, 18 Jul 2025 18:03:47 +0200
Subject: [PATCH 062/115] i386/cpu: Introduce enable_cpuid_0x1f to force
 exposing CPUID 0x1f

RH-Author: Paolo Bonzini <pbonzini@redhat.com>
RH-MergeRequest: 391: TDX support, including attestation and device assignment
RH-Jira: RHEL-15710 RHEL-20798 RHEL-49728
RH-Acked-by: Yash Mankad <None>
RH-Acked-by: Peter Xu <peterx@redhat.com>
RH-Acked-by: David Hildenbrand <david@redhat.com>
RH-Commit: [62/115] 046ef898225f70d84fbcf20266aff8478c6fb428 (bonzini/rhel-qemu-kvm)

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 wrapper 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>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/20250508150002.689633-34-xiaoyao.li@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit ab8bd85adf75900edc2764d0ebe8b53867cc54aa)
Signed-off-by: Paolo Bonzini <pbonzini@redhat.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 ee6f1c0627..ab34626b19 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -7177,7 +7177,7 @@ 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;
         }
@@ -8035,7 +8035,7 @@ 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 ee1a1b6622..83fa89bf0a 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -2168,6 +2168,9 @@ 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;
 
@@ -2429,6 +2432,12 @@ 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 4bda4f5525..f4809ee004 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -1861,7 +1861,7 @@ uint32_t kvm_x86_build_cpuid(CPUX86State *env, struct kvm_cpuid_entry2 *entries,
             break;
         }
         case 0x1f:
-            if (!x86_has_extended_topo(env->avail_cpu_topo)) {
+            if (!x86_has_cpuid_0x1f(env_archcpu(env))) {
                 cpuid_i--;
                 break;
             }
-- 
2.50.1