[PATCH v2 1/2] x86/cpufeature: Add facility to match microcode revisions

[Andi Kleen]

From: Andi Kleen <ak@xxxxxxxxxxxxxxx>

For bug workarounds or checks it is useful to check for specific
microcode versions. Add a new table format to check for steppings
with min microcode revisions.

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

Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
---
v2:
Remove all CPU match, only check boot cpu
Move INTEL_MIN_UCODE macro to header.
Minor cleanups.
Remove max ucode and driver data
---
 arch/x86/include/asm/cpu_device_id.h | 26 ++++++++++++++++++++++++++
 arch/x86/kernel/cpu/match.c          | 21 +++++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/arch/x86/include/asm/cpu_device_id.h b/arch/x86/include/asm/cpu_device_id.h
index baeba0567126..1b90bd1d0b95 100644
--- a/arch/x86/include/asm/cpu_device_id.h
+++ b/arch/x86/include/asm/cpu_device_id.h
@@ -11,4 +11,30 @@
 
 extern const struct x86_cpu_id *x86_match_cpu(const struct x86_cpu_id *match);
 
+/*
+ * Match specific microcodes
+ *
+ * vendor/family/model/stepping must be all set.
+ * min_ucode is optional and can be 0.
+ */
+
+struct x86_ucode_id {
+	u8 vendor;
+	u8 family;
+	u16 model;
+	u16 stepping;
+	u32 min_ucode;
+};
+
+#define INTEL_MIN_UCODE(mod, step, rev) {			\
+	.vendor = X86_VENDOR_INTEL,				\
+	.family = 6,						\
+	.model = mod,						\
+	.stepping = step,					\
+	.min_ucode = rev,					\
+}
+
+extern const struct x86_ucode_id *
+x86_match_ucode(const struct x86_ucode_id *match);
+
 #endif
diff --git a/arch/x86/kernel/cpu/match.c b/arch/x86/kernel/cpu/match.c
index 3fed38812eea..ec8ee31699cd 100644
--- a/arch/x86/kernel/cpu/match.c
+++ b/arch/x86/kernel/cpu/match.c
@@ -48,3 +48,24 @@ const struct x86_cpu_id *x86_match_cpu(const struct x86_cpu_id *match)
 	return NULL;
 }
 EXPORT_SYMBOL(x86_match_cpu);
+
+const struct x86_ucode_id *x86_match_ucode(const struct x86_ucode_id *match)
+{
+	struct cpuinfo_x86 *c = &boot_cpu_data;
+	const struct x86_ucode_id *m;
+
+	for (m = match; m->vendor | m->family | m->model; m++) {
+		if (c->x86_vendor != m->vendor)
+			continue;
+		if (c->x86 != m->family)
+			continue;
+		if (c->x86_model != m->model)
+			continue;
+		if (c->x86_stepping != m->stepping)
+			continue;
+		if (c->microcode < m->min_ucode)
+			continue;
+		return m;
+	}
+	return NULL;
+}
-- 
2.17.1