x86/microcode: Make sure boot_cpu_data.microcode is up-to-date

BugLink: https://bugs.launchpad.net/bugs/1830176

commit 370a132b upstream.

When preparing an MCE record for logging, boot_cpu_data.microcode is used
to read out the microcode revision on the box.

However, on systems where late microcode update has happened, the microcode
revision output in a MCE log record is wrong because
boot_cpu_data.microcode is not updated when the microcode gets updated.

But, the microcode revision saved in boot_cpu_data's microcode member
should be kept up-to-date, regardless, for consistency.

Make it so.

Fixes: fa94d0c6 ("x86/MCE: Save microcode revision in machine check records")
Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: sironi@amazon.de
Link: http://lkml.kernel.org/r/20180731112739.32338-1-prarit@redhat.com
[bwh: Backported to 4.4: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

arch/x86/kernel/cpu/microcode/amd.c

@@ -712,6 +712,10 @@ int apply_microcode_amd(int cpu)
 	uci->cpu_sig.rev = mc_amd->hdr.patch_id;
 	c->microcode = mc_amd->hdr.patch_id;
 
+	/* Update boot_cpu_data's revision too, if we're on the BSP: */
+	if (c->cpu_index == boot_cpu_data.cpu_index)
+		boot_cpu_data.microcode = mc_amd->hdr.patch_id;
+
 	return 0;
 }
 

arch/x86/kernel/cpu/microcode/intel.c

@@ -905,6 +905,10 @@ static int apply_microcode_intel(int cpu)
 	uci->cpu_sig.rev = rev;
 	c->microcode = rev;
 
+	/* Update boot_cpu_data's revision too, if we're on the BSP: */
+	if (c->cpu_index == boot_cpu_data.cpu_index)
+		boot_cpu_data.microcode = rev;
+
 	return 0;
 }