[PATCH 3.16 178/328] x86/microcode: Make sure boot_cpu_data.microcode is up-to-date

[Ben Hutchings]

3.16.62-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Prarit Bhargava <prarit@xxxxxxxxxx>

commit 370a132bb2227ff76278f98370e0e701d86ff752 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: fa94d0c6e0f3 ("x86/MCE: Save microcode revision in machine check records")
Signed-off-by: Prarit Bhargava <prarit@xxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Cc: sironi@xxxxxxxxx
Link: http://lkml.kernel.org/r/20180731112739.32338-1-prarit@xxxxxxxxxx
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 arch/x86/kernel/cpu/microcode/amd.c   | 4 ++++
 arch/x86/kernel/cpu/microcode/intel.c | 4 ++++
 2 files changed, 8 insertions(+)

--- a/arch/x86/kernel/cpu/microcode/amd.c
+++ b/arch/x86/kernel/cpu/microcode/amd.c
@@ -231,6 +231,10 @@ 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;
 }
 
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -188,6 +188,10 @@ int apply_microcode(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;
 }