[PATCH 5/6] x86/match-cpu: Support matching on steppings

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Architecturally, stepping is a 4-bit field, so a uint16_t suffices for a
bitmap of steppings.

In order to keep the size of struct x86_cpu_id the same, shrink the vendor and
family fields, neither of which need to be uint16_t in Xen.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Linux supports all fields being optional.  This has lead to using
X86_MATCH_CPU(ANY, ANY, ANY, ANY, FEATURE_FOO, NULL) in place of
boot_cpu_has(), and is not a construct I think we want to encorage.
---
 xen/arch/x86/cpu/common.c            |  4 +++-
 xen/arch/x86/include/asm/match-cpu.h | 12 ++++++++----
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c
index cc004fc976f5..fc25935d3109 100644
--- a/xen/arch/x86/cpu/common.c
+++ b/xen/arch/x86/cpu/common.c
@@ -1003,13 +1003,15 @@ const struct x86_cpu_id *x86_match_cpu(const struct 
x86_cpu_id table[])
        const struct x86_cpu_id *m;
        const struct cpuinfo_x86 *c = &boot_cpu_data;
 
-       for (m = table; m->vendor | m->family | m->model | m->feature; m++) {
+       for (m = table; m->vendor | m->family | m->model | m->steppings | 
m->feature; m++) {
                if (c->x86_vendor != m->vendor)
                        continue;
                if (c->x86 != m->family)
                        continue;
                if (c->x86_model != m->model)
                        continue;
+               if (m->steppings && !(m->steppings & (1U << c->stepping)))
+                       continue;
                if (!cpu_has(c, m->feature))
                        continue;
                return m;
diff --git a/xen/arch/x86/include/asm/match-cpu.h 
b/xen/arch/x86/include/asm/match-cpu.h
index dcdc50a70d14..3862e766ccfc 100644
--- a/xen/arch/x86/include/asm/match-cpu.h
+++ b/xen/arch/x86/include/asm/match-cpu.h
@@ -8,28 +8,32 @@
 #include <asm/intel-family.h>
 #include <asm/x86-vendors.h>
 
+#define X86_STEPPINGS_ANY 0
 #define X86_FEATURE_ANY X86_FEATURE_LM
 
 struct x86_cpu_id {
-    uint16_t vendor;
-    uint16_t family;
+    uint8_t vendor;
+    uint8_t family;
     uint16_t model;
+    uint16_t steppings; /* Stepping bitmap, or X86_STEPPINGS_ANY */
     uint16_t feature;   /* X86_FEATURE_*, or X86_FEATURE_ANY */
     const void *driver_data;
 };
 
-#define X86_MATCH_CPU(v, f, m, feat, data)                      \
+#define X86_MATCH_CPU(v, f, m, steps, feat, data)               \
     {                                                           \
         .vendor       = (v),                                    \
         .family       = (f),                                    \
         .model        = (m),                                    \
+        .steppings    = (steps),                                \
         .feature      = (feat),                                 \
         .driver_data  = (const void *)(unsigned long)(data),    \
     }
 
 #define X86_MATCH_VFM(vfm, data)                                \
     X86_MATCH_CPU(VFM_VENDOR(vfm), VFM_FAMILY(vfm),             \
-                  VFM_MODEL(vfm), X86_FEATURE_ANY, data)
+                  VFM_MODEL(vfm), X86_STEPPINGS_ANY,            \
+                  X86_FEATURE_ANY, data)
 
 /*
  * x86_match_cpu() - match the CPU against an array of x86_cpu_ids[]
-- 
2.39.5