[PATCH 4.15 116/168] x86/microcode/intel: Look into the patch cache first

From: Greg Kroah-Hartman
Date: Tue Apr 10 2018 - 18:31:57 EST


4.15-stable review patch. If anyone has any objections, please let me know.

------------------

From: Borislav Petkov <bp@xxxxxxx>

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@xxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Tested-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
Tested-by: Ashok Raj <ashok.raj@xxxxxxxxx>
Cc: Arjan Van De Ven <arjan.van.de.ven@xxxxxxxxx>
Link: https://lkml.kernel.org/r/20180228102846.13447-6-bp@xxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
arch/x86/kernel/cpu/microcode/intel.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)

--- 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,

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_
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;
}