[Patch v5 5/5] x86/microcode/intel: Print old and new rev during early boot

[Ashok Raj <ashok.raj@intel.com>]

Make early loading message to match late loading messages. Print
both old and new revisions.

This is helpful to know what the BIOS loaded revision is before an early
update.

New dmesg log is shown below.

microcode: early update: 0x2b000041 -> 0x2b000070 date = 2000-01-01

Cache the early BIOS revision before the microcode update and change the
print_ucode_info() so it prints both the old and new revision in the same
format as microcode_reload_late().

Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>
Cc: x86 <x86@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Alison Schofield <alison.schofield@intel.com>
Cc: Reinette Chatre <reinette.chatre@intel.com>
Cc: Thomas Gleixner (Intel) <tglx@linutronix.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Stefan Talpalaru <stefantalpalaru@yahoo.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Rafael J. Wysocki <rafael@kernel.org>
Cc: Peter Zilstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Andrew Cooper <Andrew.Cooper3@citrix.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
---
Updates since V1:

Thomas: Commit log updates as suggested.
---
 arch/x86/kernel/cpu/microcode/intel.c | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index 146a60a9449a..4471d418f28a 100644
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -310,10 +310,10 @@ static bool load_builtin_intel_microcode(struct cpio_data *cp)
 /*
  * Print ucode update info.
  */
-static void print_ucode_info(unsigned int new_rev, unsigned int date)
+static void print_ucode_info(int old_rev, int new_rev, unsigned int date)
 {
-	pr_info_once("microcode updated early to revision 0x%x, date = %04x-%02x-%02x\n",
-		     new_rev, date & 0xffff, date >> 24,
+	pr_info_once("early update: 0x%x -> 0x%x, date = %04x-%02x-%02x\n",
+		     old_rev, new_rev, date & 0xffff, date >> 24,
 		     (date >> 16) & 0xff);
 }
 
@@ -321,6 +321,7 @@ static void print_ucode_info(unsigned int new_rev, unsigned int date)
 
 static int delay_ucode_info;
 static int current_mc_date;
+static int early_old_rev;
 
 /*
  * Print early updated ucode info after printk works. This is delayed info dump.
@@ -331,7 +332,7 @@ void show_ucode_info_early(void)
 
 	if (delay_ucode_info) {
 		intel_cpu_collect_info(&uci);
-		print_ucode_info(uci.cpu_sig.rev, current_mc_date);
+		print_ucode_info(early_old_rev, uci.cpu_sig.rev, current_mc_date);
 		delay_ucode_info = 0;
 	}
 }
@@ -340,29 +341,32 @@ void show_ucode_info_early(void)
  * At this point, we can not call printk() yet. Delay printing microcode info in
  * show_ucode_info_early() until printk() works.
  */
-static void print_ucode(int new_rev, int date)
+static void print_ucode(int old_rev, int new_rev, int date)
 {
 	int *delay_ucode_info_p;
 	int *current_mc_date_p;
+	int *early_old_rev_p;
 
 	delay_ucode_info_p = (int *)__pa_nodebug(&delay_ucode_info);
 	current_mc_date_p = (int *)__pa_nodebug(&current_mc_date);
+	early_old_rev_p = (int *)__pa_nodebug(&early_old_rev);
 
 	*delay_ucode_info_p = 1;
 	*current_mc_date_p = date;
+	*early_old_rev_p = old_rev;
 }
 #else
 
-static inline void print_ucode(int new_rev, int date)
+static inline void print_ucode(int old_rev, int new_rev, int date)
 {
-	print_ucode_info(new_rev, date);
+	print_ucode_info(old_rev, new_rev, date);
 }
 #endif
 
 static int apply_microcode_early(struct ucode_cpu_info *uci, bool early)
 {
 	struct microcode_intel *mc;
-	u32 rev;
+	u32 rev, old_rev;
 
 	mc = uci->mc;
 	if (!mc)
@@ -388,6 +392,7 @@ static int apply_microcode_early(struct ucode_cpu_info *uci, bool early)
 	/* write microcode via MSR 0x79 */
 	native_wrmsrl(MSR_IA32_UCODE_WRITE, (unsigned long)mc->bits);
 
+	old_rev = rev;
 	rev = intel_get_microcode_revision();
 	if (rev != mc->hdr.rev)
 		return -1;
@@ -395,9 +400,9 @@ static int apply_microcode_early(struct ucode_cpu_info *uci, bool early)
 	uci->cpu_sig.rev = rev;
 
 	if (early)
-		print_ucode(uci->cpu_sig.rev, mc->hdr.date);
+		print_ucode(old_rev, uci->cpu_sig.rev, mc->hdr.date);
 	else
-		print_ucode_info(uci->cpu_sig.rev, mc->hdr.date);
+		print_ucode_info(old_rev, uci->cpu_sig.rev, mc->hdr.date);
 
 	return 0;
 }
-- 
2.34.1