x86, ucode-amd: Ensure ucode update on suspend/resume after CPU off/online cycle

When switching a CPU offline/online and then doing
suspend/resume, ucode is not updated on this CPU.

This is due to the microcode_fini_cpu() call which frees uci->mc
when setting the CPU offline:

  static void microcode_fini_cpu_amd(int cpu)
  {
          struct ucode_cpu_info *uci = ucode_cpu_info + cpu;

          vfree(uci->mc);
          uci->mc = NULL;
  }

When the CPU is set online uci->mc is still NULL because no
ucode update is required.

Finally this prevents ucode update when resuming after suspend:

  static enum ucode_state microcode_resume_cpu(int cpu)
  {
        struct ucode_cpu_info *uci = ucode_cpu_info + cpu;

        if (!uci->mc)
                return UCODE_NFOUND;

        ...
  }

Fix is to check whether uci->mc is valid before
microcode_resume_cpu() is called.

Signed-off-by: Andreas Herrmann <[email protected]>
Cc: dimm <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>

arch/x86/kernel/microcode_core.c

@@ -393,7 +393,7 @@ static enum ucode_state microcode_update_cpu(int cpu)
 	struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
 	enum ucode_state ustate;
 
-	if (uci->valid)
+	if (uci->valid && uci->mc)
 		ustate = microcode_resume_cpu(cpu);
 	else
 		ustate = microcode_init_cpu(cpu);