[PATCH 4.14 086/138] x86/CPU: Add a microcode loader callback

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

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

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

From: Borislav Petkov <bp@xxxxxxx>

commit 1008c52c09dcb23d93f8e0ea83a6246265d2cce0 upstream.

Add a callback function which the microcode loader calls when microcode
has been updated to a newer revision. Do the callback only when no error
was encountered during loading.

Tested-by: Ashok Raj <ashok.raj@xxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Reviewed-by: Ashok Raj <ashok.raj@xxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20180216112640.11554-3-bp@xxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/x86/include/asm/processor.h     |    1 +
 arch/x86/kernel/cpu/common.c         |   10 ++++++++++
 arch/x86/kernel/cpu/microcode/core.c |    8 ++++++--
 3 files changed, 17 insertions(+), 2 deletions(-)

--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -968,4 +968,5 @@ bool xen_set_default_idle(void);
 
 void stop_this_cpu(void *dummy);
 void df_debug(struct pt_regs *regs, long error_code);
+void microcode_check(void);
 #endif /* _ASM_X86_PROCESSOR_H */
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1724,3 +1724,13 @@ static int __init init_cpu_syscore(void)
 	return 0;
 }
 core_initcall(init_cpu_syscore);
+
+/*
+ * The microcode loader calls this upon late microcode load to recheck features,
+ * only when microcode has been updated. Caller holds microcode_mutex and CPU
+ * hotplug lock.
+ */
+void microcode_check(void)
+{
+	perf_check_microcode();
+}
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -509,6 +509,7 @@ static ssize_t reload_store(struct devic
 			    const char *buf, size_t size)
 {
 	enum ucode_state tmp_ret = UCODE_OK;
+	bool do_callback = false;
 	unsigned long val;
 	ssize_t ret = 0;
 	int cpu;
@@ -531,10 +532,13 @@ static ssize_t reload_store(struct devic
 			if (!ret)
 				ret = -EINVAL;
 		}
+
+		if (tmp_ret == UCODE_UPDATED)
+			do_callback = true;
 	}
 
-	if (!ret && tmp_ret == UCODE_UPDATED)
-		perf_check_microcode();
+	if (!ret && do_callback)
+		microcode_check();
 
 	mutex_unlock(&microcode_mutex);
 	put_online_cpus();