[PATCH 3/3] x86/Intel: use CPUID bit to determine PPIN availability

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

From: Jan Beulich <jbeulich@xxxxxxxx>

As of SDM revision 076 there is a CPUID bit for this functionality. Use
it to amend the existing model-based logic.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>

Split in two.
---
 tools/misc/xen-cpuid.c                      |  1 +
 xen/arch/x86/cpu/mcheck/mce_intel.c         | 10 +++++++++-
 xen/include/public/arch-x86/cpufeatureset.h |  1 +
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/tools/misc/xen-cpuid.c b/tools/misc/xen-cpuid.c
index 17e67e379fa4..3c8f3ed1bad1 100644
--- a/tools/misc/xen-cpuid.c
+++ b/tools/misc/xen-cpuid.c
@@ -197,6 +197,7 @@ static const char *const str_e21a[32] =
 
 static const char *const str_7b1[32] =
 {
+    [ 0] = "ppin",
 };
 
 static const struct {
diff --git a/xen/arch/x86/cpu/mcheck/mce_intel.c 
b/xen/arch/x86/cpu/mcheck/mce_intel.c
index d0161e9d4daa..d63d6083d3a7 100644
--- a/xen/arch/x86/cpu/mcheck/mce_intel.c
+++ b/xen/arch/x86/cpu/mcheck/mce_intel.c
@@ -859,12 +859,20 @@ static void intel_init_ppin(const struct cpuinfo_x86 *c)
     /*
      * Even if testing the presence of the MSR would be enough, we don't
      * want to risk the situation where other models reuse this MSR for
-     * other purposes.
+     * other purposes.  Despite the late addition of a CPUID bit (rendering
+     * the MSR architectural), keep using the same detection logic there.
      */
     switch ( c->x86_model )
     {
         uint64_t val;
 
+    default:
+        if ( !cpu_has(c, X86_FEATURE_INTEL_PPIN) )
+        {
+            ppin_msr = 0;
+            return;
+        }
+        fallthrough;
     case 0x3e: /* IvyBridge X */
     case 0x3f: /* Haswell X */
     case 0x4f: /* Broadwell X */
diff --git a/xen/include/public/arch-x86/cpufeatureset.h 
b/xen/include/public/arch-x86/cpufeatureset.h
index 588f924de59e..6e44148a0901 100644
--- a/xen/include/public/arch-x86/cpufeatureset.h
+++ b/xen/include/public/arch-x86/cpufeatureset.h
@@ -300,6 +300,7 @@ XEN_CPUFEATURE(LFENCE_DISPATCH,    11*32+ 2) /*A  LFENCE 
always serializing */
 XEN_CPUFEATURE(NSCB,               11*32+ 6) /*A  Null Selector Clears Base 
(and limit too) */
 
 /* Intel-defined CPU features, CPUID level 0x00000007:1.ebx, word 12 */
+XEN_CPUFEATURE(INTEL_PPIN,         12*32+ 0) /*   Protected Processor 
Inventory Number */
 
 #endif /* XEN_CPUFEATURE */
 
-- 
2.11.0