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From: Andrew Cooper <andrew.cooper3@citrix.com>
Subject: x86/msr: Definitions for MSR_INTEL_CORE_THREAD_COUNT

This is a model specific register which details the current configuration
cores and threads in the package.  Because of how Hyperthread and Core
configuration works works in firmware, the MSR it is de-facto constant and
will remain unchanged until the next system reset.

It is a read only MSR (so unilaterally reject writes), but for now retain its
leaky-on-read properties.  Further CPUID/MSR work is required before we can
start virtualising a consistent topology to the guest, and retaining the old
behaviour is the safest course of action.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>

diff --git a/xen/arch/x86/msr.c b/xen/arch/x86/msr.c
index b49fbd8..153f36b 100644
--- a/xen/arch/x86/msr.c
+++ b/xen/arch/x86/msr.c
@@ -180,6 +180,10 @@ int guest_rdmsr(const struct vcpu *v, uint32_t msr, uint64_t *val)
                _MSR_MISC_FEATURES_CPUID_FAULTING;
         break;
 
+        /*
+         * TODO: Implement when we have better topology representation.
+    case MSR_INTEL_CORE_THREAD_COUNT:
+         */
     default:
         return X86EMUL_UNHANDLEABLE;
     }
@@ -202,6 +206,7 @@ int guest_wrmsr(struct vcpu *v, uint32_t msr, uint64_t val)
     {
         uint64_t rsvd;
 
+    case MSR_INTEL_CORE_THREAD_COUNT:
     case MSR_INTEL_PLATFORM_INFO:
     case MSR_ARCH_CAPABILITIES:
         /* Read-only */
diff --git a/xen/include/asm-x86/msr-index.h b/xen/include/asm-x86/msr-index.h
index 7588fc1..7cddfca 100644
--- a/xen/include/asm-x86/msr-index.h
+++ b/xen/include/asm-x86/msr-index.h
@@ -34,6 +34,10 @@
 #define EFER_KNOWN_MASK		(EFER_SCE | EFER_LME | EFER_LMA | EFER_NX | \
 				 EFER_SVME | EFER_LMSLE | EFER_FFXSE)
 
+#define MSR_INTEL_CORE_THREAD_COUNT     0x00000035
+#define MSR_CTC_THREAD_MASK             0x0000ffff
+#define MSR_CTC_CORE_MASK               0xffff0000
+
 /* Speculation Controls. */
 #define MSR_SPEC_CTRL			0x00000048
 #define SPEC_CTRL_IBRS			(_AC(1, ULL) << 0)