[PATCH 6/6] DO NOT APPLY: Example breakage

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Prior to disentangling X86_NR_FEAT from FEATURESET_NR_ENTRIES, GCC 12
correctly notices:

  lib/x86/cpuid.c: In function 'x86_cpu_policy_to_featureset':
  lib/x86/cpuid.c:82:7: error: array subscript 16 is outside array bounds of 
'uint32_t[16]' {aka 'unsigned int[16]'} [-Werror=array-bounds=]
     82 |     fs[FEATURESET_7a2]       = p->feat._7a2;
        |     ~~^~~~~~~~~~~~~~~~
  lib/x86/cpuid.c:64:42: note: at offset 64 into object 'fs' of size [0, 64]

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/include/xen/lib/x86/cpu-policy.h   | 6 +++++-
 xen/include/xen/lib/x86/cpuid-consts.h | 2 ++
 xen/lib/x86/cpuid.c                    | 2 ++
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/xen/include/xen/lib/x86/cpu-policy.h 
b/xen/include/xen/lib/x86/cpu-policy.h
index 01431de056c8..164b3f4aac13 100644
--- a/xen/include/xen/lib/x86/cpu-policy.h
+++ b/xen/include/xen/lib/x86/cpu-policy.h
@@ -192,7 +192,11 @@ struct cpu_policy
             };
 
             /* Subleaf 2. */
-            uint32_t /* a */:32, /* b */:32, /* c */:32;
+            union {
+                uint32_t _7a2;
+                struct { DECL_BITFIELD(7a2); };
+            };
+            uint32_t /* b */:32, /* c */:32;
             union {
                 uint32_t _7d2;
                 struct { DECL_BITFIELD(7d2); };
diff --git a/xen/include/xen/lib/x86/cpuid-consts.h 
b/xen/include/xen/lib/x86/cpuid-consts.h
index 9fe931b8e31f..5dd9727fec79 100644
--- a/xen/include/xen/lib/x86/cpuid-consts.h
+++ b/xen/include/xen/lib/x86/cpuid-consts.h
@@ -20,8 +20,10 @@
 #define FEATURESET_7d2   13 /* 0x00000007:2.edx    */
 #define FEATURESET_7c1   14 /* 0x00000007:1.ecx    */
 #define FEATURESET_7d1   15 /* 0x00000007:1.edx    */
+#define FEATURESET_7a2   16
 
 #define X86_NR_FEAT (FEATURESET_7d1 + 1)
+//#define X86_NR_FEAT (FEATURESET_7a2 + 1)
 
 #endif /* !XEN_LIB_X86_CONSTS_H */
 
diff --git a/xen/lib/x86/cpuid.c b/xen/lib/x86/cpuid.c
index 76f26e92af8d..90bc82a18c30 100644
--- a/xen/lib/x86/cpuid.c
+++ b/xen/lib/x86/cpuid.c
@@ -79,6 +79,7 @@ void x86_cpu_policy_to_featureset(
     fs[FEATURESET_7d2]       = p->feat._7d2;
     fs[FEATURESET_7c1]       = p->feat._7c1;
     fs[FEATURESET_7d1]       = p->feat._7d1;
+    fs[FEATURESET_7a2]       = p->feat._7a2;
 }
 
 void x86_cpu_featureset_to_policy(
@@ -100,6 +101,7 @@ void x86_cpu_featureset_to_policy(
     p->feat._7d2             = fs[FEATURESET_7d2];
     p->feat._7c1             = fs[FEATURESET_7c1];
     p->feat._7d1             = fs[FEATURESET_7d1];
+    p->feat._7a2             = fs[FEATURESET_7a2];
 }
 
 void x86_cpu_policy_recalc_synth(struct cpu_policy *p)
-- 
2.30.2