From: Vladislav Yaroshchuk <yaroshchuk2000@gmail.com>

Some guests (ex. Darwin-XNU) can attemp to read this MSR to retrieve and
validate CPU topology comparing it to ACPI MADT content

MSR description from Intel Manual:
35H: MSR_CORE_THREAD_COUNT: Configured State of Enabled Processor Core
  Count and Logical Processor Count

Bits 15:0 THREAD_COUNT The number of logical processors that are
  currently enabled in the physical package

Bits 31:16 Core_COUNT The number of processor cores that are currently
  enabled in the physical package

Bits 63:32 Reserved

Signed-off-by: Vladislav Yaroshchuk <yaroshchuk2000@gmail.com>
Message-Id: <20210113205323.33310-1-yaroshchuk2000@gmail.com>
[RB: reordered MSR definition and dropped u suffix from shift offset]
Signed-off-by: Roman Bolshakov <r.bolshakov@yadro.com>
---
 target/i386/cpu.h         | 1 +
 target/i386/hvf/x86_emu.c | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index d23a5b340a..e2fe0689cc 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -366,6 +366,7 @@ typedef enum X86Seg {
 
 #define MSR_IA32_SMBASE                 0x9e
 #define MSR_SMI_COUNT                   0x34
+#define MSR_CORE_THREAD_COUNT           0x35
 #define MSR_MTRRcap                     0xfe
 #define MSR_MTRRcap_VCNT                8
 #define MSR_MTRRcap_FIXRANGE_SUPPORT    (1 << 8)
diff --git a/target/i386/hvf/x86_emu.c b/target/i386/hvf/x86_emu.c
index da570e352b..e52c39ddb1 100644
--- a/target/i386/hvf/x86_emu.c
+++ b/target/i386/hvf/x86_emu.c
@@ -668,6 +668,7 @@ void simulate_rdmsr(struct CPUState *cpu)
 {
     X86CPU *x86_cpu = X86_CPU(cpu);
     CPUX86State *env = &x86_cpu->env;
+    CPUState *cs = env_cpu(env);
     uint32_t msr = ECX(env);
     uint64_t val = 0;
 
@@ -745,6 +746,10 @@ void simulate_rdmsr(struct CPUState *cpu)
     case MSR_MTRRdefType:
         val = env->mtrr_deftype;
         break;
+    case MSR_CORE_THREAD_COUNT:
+        val = cs->nr_threads * cs->nr_cores; /* thread count, bits 15..0 */
+        val |= ((uint32_t)cs->nr_cores << 16); /* core count, bits 31..16 */
+        break;
     default:
         /* fprintf(stderr, "%s: unknown msr 0x%x\n", __func__, msr); */
         val = 0;
-- 
2.30.0