linux-kernel - [4.15 & 4.14 stable 08/12] x86/microcode/intel: Look into the patch cache first

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Date:   Fri,  6 Apr 2018 11:30:22 -0700
From:   Ashok Raj <ashok.raj@...el.com>
To:     gregkh@...uxfoundation.org, tglx@...utronix.de
Cc:     Borislav Petkov <bp@...e.de>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, thomas.lendacky@....com,
        arjan.van.de.ven@...el.com, asit.k.mallick@...el.com
Subject: [4.15 & 4.14 stable 08/12] x86/microcode/intel: Look into the patch cache first

From: Borislav Petkov <bp@...e.de>

commit d8c3b52c00a05036e0a6b315b4b17921a7b67997 upstream

The cache might contain a newer patch - look in there first.

A follow-on change will make sure newest patches are loaded into the
cache of microcode patches.

Signed-off-by: Borislav Petkov <bp@...e.de>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Tested-by: Tom Lendacky <thomas.lendacky@....com>
Tested-by: Ashok Raj <ashok.raj@...el.com>
Cc: Arjan Van De Ven <arjan.van.de.ven@...el.com>
Cc: Tom Lendacky <thomas.lendacky@....com>
Cc: Asit K Mallick <asit.k.mallick@...el.com>
Cc: stable@...r.kernel.org
Link: https://lkml.kernel.org/r/20180228102846.13447-6-bp@alien8.de
---
 arch/x86/kernel/cpu/microcode/intel.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index e2864bc..2aded9d 100644
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -791,9 +791,9 @@ static int collect_cpu_info(int cpu_num, struct cpu_signature *csig)
 
 static enum ucode_state apply_microcode_intel(int cpu)
 {
-	struct microcode_intel *mc;
-	struct ucode_cpu_info *uci;
+	struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
 	struct cpuinfo_x86 *c = &cpu_data(cpu);
+	struct microcode_intel *mc;
 	static int prev_rev;
 	u32 rev;
 
@@ -801,11 +801,10 @@ static enum ucode_state apply_microcode_intel(int cpu)
 	if (WARN_ON(raw_smp_processor_id() != cpu))
 		return UCODE_ERROR;
 
-	uci = ucode_cpu_info + cpu;
-	mc = uci->mc;
+	/* Look for a newer patch in our cache: */
+	mc = find_patch(uci);
 	if (!mc) {
-		/* Look for a newer patch in our cache: */
-		mc = find_patch(uci);
+		mc = uci->mc;
 		if (!mc)
 			return UCODE_NFOUND;
 	}
-- 
2.7.4