linux-kernel - [PATCH v1 1/2] x86/cpufeature: Add facility to match microcode revisions

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Date:   Fri,  5 Oct 2018 17:19:27 -0700
From:   Andi Kleen <andi@...stfloor.org>
To:     peterz@...radead.org
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, eranian@...gle.com,
        kan.liang@...el.com, isaku.yamahata@...el.com, kvm@...r.kernel.org,
        Andi Kleen <ak@...ux.intel.com>
Subject: [PATCH v1 1/2] x86/cpufeature: Add facility to match microcode revisions

From: Andi Kleen <ak@...ux.intel.com>

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/max 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@...ux.intel.com>
---
 arch/x86/include/asm/cpu_device_id.h | 22 ++++++++++++++
 arch/x86/kernel/cpu/match.c          | 43 ++++++++++++++++++++++++++++
 2 files changed, 65 insertions(+)

diff --git a/arch/x86/include/asm/cpu_device_id.h b/arch/x86/include/asm/cpu_device_id.h
index baeba0567126..bf2222d5438c 100644
--- a/arch/x86/include/asm/cpu_device_id.h
+++ b/arch/x86/include/asm/cpu_device_id.h
@@ -11,4 +11,26 @@
 
 extern const struct x86_cpu_id *x86_match_cpu(const struct x86_cpu_id *match);
 
+/*
+ * Match specific microcodes or steppings.
+ *
+ * vendor/family/model/stepping must be all set.
+ * min_ucode/max_ucode/driver_data are optional and can be 0.
+ */
+
+struct x86_ucode_id {
+	__u16 vendor;
+	__u16 family;
+	__u16 model;
+	__u16 stepping;
+	__u32 min_ucode;
+	__u32 max_ucode;
+	kernel_ulong_t driver_data;
+};
+
+extern const struct x86_ucode_id *
+x86_match_ucode_cpu(int cpu, const struct x86_ucode_id *match);
+extern const struct x86_ucode_id *
+x86_match_ucode_all(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..f29a21b2809c 100644
--- a/arch/x86/kernel/cpu/match.c
+++ b/arch/x86/kernel/cpu/match.c
@@ -48,3 +48,46 @@ 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_cpu(int cpu,
+					       const struct x86_ucode_id *match)
+{
+	const struct x86_ucode_id *m;
+	struct cpuinfo_x86 *c = &cpu_data(cpu);
+
+	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 (m->min_ucode && c->microcode < m->min_ucode)
+			continue;
+		if (m->max_ucode && c->microcode > m->max_ucode)
+			continue;
+		return m;
+	}
+	return NULL;
+}
+
+/* Check all CPUs */
+const struct x86_ucode_id *x86_match_ucode_all(const struct x86_ucode_id *match)
+{
+	int cpu;
+	const struct x86_ucode_id *all_m = NULL;
+	bool first = true;
+
+	for_each_online_cpu(cpu) {
+		const struct x86_ucode_id *m = x86_match_ucode_cpu(cpu, match);
+
+		if (first)
+			all_m = m;
+		else if (m != all_m)
+			return NULL;
+		first = false;
+	}
+	return all_m;
+}
-- 
2.17.1