x86/cpufeature: Add facility to check for min microcode revisions

For bug workarounds or checks, it is useful to check for specific
microcode revisions.

Add a new generic function to match the CPU with stepping.
Add the other function to check the min microcode revisions for
the matched CPU.

A new table format is introduced to facilitate the quirk to
fill the related information.

This does not change the existing x86_cpu_id because it's an ABI
shared with modules, and also has quite different requirements,
as in no wildcards, but everything has to be matched exactly.

Originally-by: Andi Kleen <ak@linux.intel.com>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: eranian@google.com
Link: https://lkml.kernel.org/r/1549319013-4522-1-git-send-email-kan.liang@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/include/asm/cpu_device_id.h b/arch/x86/include/asm/cpu_device_id.h
index baeba05671268cc7d835ecf6decbfc9fc5fc93ea..3417110574c12212f7185213bfe566ac2b541a1e 100644 (file)
--- a/arch/x86/include/asm/cpu_device_id.h
+++ b/arch/x86/include/asm/cpu_device_id.h
@@ -11,4 +11,32 @@
 
 extern const struct x86_cpu_id *x86_match_cpu(const struct x86_cpu_id *match);
 
+/*
+ * Match specific microcode revisions.
+ *
+ * vendor/family/model/stepping must be all set.
+ *
+ * Only checks against the boot CPU.  When mixed-stepping configs are
+ * valid for a CPU model, add a quirk for every valid stepping and
+ * do the fine-tuning in the quirk handler.
+ */
+
+struct x86_cpu_desc {
+       __u8    x86_family;
+       __u8    x86_vendor;
+       __u8    x86_model;
+       __u8    x86_stepping;
+       __u32   x86_microcode_rev;
+};
+
+#define INTEL_CPU_DESC(mod, step, rev) {                       \
+       .x86_family = 6,                                        \
+       .x86_vendor = X86_VENDOR_INTEL,                         \
+       .x86_model = mod,                                       \
+       .x86_stepping = step,                                   \
+       .x86_microcode_rev = rev,                               \
+}
+
+extern bool x86_cpu_has_min_microcode_rev(const struct x86_cpu_desc *table);
+
 #endif

diff --git a/arch/x86/kernel/cpu/match.c b/arch/x86/kernel/cpu/match.c
index 3fed38812eea340ff1ca2adb4b47534de1e73a59..6dd78d8235e4498abe83b624d69f9104315ae56e 100644 (file)
--- a/arch/x86/kernel/cpu/match.c
+++ b/arch/x86/kernel/cpu/match.c
@@ -48,3 +48,34 @@ const struct x86_cpu_id *x86_match_cpu(const struct x86_cpu_id *match)
        return NULL;
 }
 EXPORT_SYMBOL(x86_match_cpu);
+
+static const struct x86_cpu_desc *
+x86_match_cpu_with_stepping(const struct x86_cpu_desc *match)
+{
+       struct cpuinfo_x86 *c = &boot_cpu_data;
+       const struct x86_cpu_desc *m;
+
+       for (m = match; m->x86_family | m->x86_model; m++) {
+               if (c->x86_vendor != m->x86_vendor)
+                       continue;
+               if (c->x86 != m->x86_family)
+                       continue;
+               if (c->x86_model != m->x86_model)
+                       continue;
+               if (c->x86_stepping != m->x86_stepping)
+                       continue;
+               return m;
+       }
+       return NULL;
+}
+
+bool x86_cpu_has_min_microcode_rev(const struct x86_cpu_desc *table)
+{
+       const struct x86_cpu_desc *res = x86_match_cpu_with_stepping(table);
+
+       if (!res || res->x86_microcode_rev > boot_cpu_data.microcode)
+               return false;
+
+       return true;
+}
+EXPORT_SYMBOL_GPL(x86_cpu_has_min_microcode_rev);