[PATCH] x86/microcode: Print previous version of microcode after reload

[PATCH] x86/microcode: Print previous version of microcode after reload

[Ashok Raj]

It will be useful to print both old and new versions of microcode after a
reload is complete.

Signed-off-by: Ashok Raj <ashok.raj@intel.com>
---
 arch/x86/kernel/cpu/microcode/core.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index ad57e0e4d674..6a41cee242f6 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -491,7 +491,7 @@ static int __reload_late(void *info)
  */
 static int microcode_reload_late(void)
 {
-	int ret;
+	int old = boot_cpu_data.microcode, ret;
 
 	pr_err("Attempting late microcode loading - it is dangerous and taints the kernel.\n");
 	pr_err("You should switch to early loading, if possible.\n");
@@ -503,7 +503,8 @@ static int microcode_reload_late(void)
 	if (ret == 0)
 		microcode_check();
 
-	pr_info("Reload completed, microcode revision: 0x%x\n", boot_cpu_data.microcode);
+	pr_info("Reload completed, microcode revision: 0x%x -> 0x%x\n",
+		old, boot_cpu_data.microcode);
 
 	return ret;
 }
-- 
2.32.0

RE: [PATCH] x86/microcode: Print previous version of microcode after reload

[Luck, Tony]

> It will be useful to print both old and new versions of microcode after a
> reload is complete.

Yes, yes, yes! Many times I've had to dig deep to figure out what base microcode
was loaded by the BIOS because the early init update doesn't say what the old
version was.

Acked-by: Tony Luck <tony.luck@intel.com>

-Tony

[tip: x86/microcode] x86/microcode: Print previous version of microcode after reload

[tip-bot2 for Ashok Raj]

The following commit has been merged into the x86/microcode branch of tip:

Commit-ID:     7fce8d6eccbc31a561d07c79f359ad09f0424347
Gitweb:        https://git.kernel.org/tip/7fce8d6eccbc31a561d07c79f359ad09f0424347
Author:        Ashok Raj <ashok.raj@intel.com>
AuthorDate:    Mon, 29 Aug 2022 18:10:30 
Committer:     Borislav Petkov <bp@suse.de>
CommitterDate: Fri, 02 Sep 2022 08:01:58 +02:00

x86/microcode: Print previous version of microcode after reload

Print both old and new versions of microcode after a reload is complete
because knowing the previous microcode version is sometimes important
from a debugging perspective.

  [ bp: Massage commit message. ]

Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Tony Luck <tony.luck@intel.com>
Link: https://lore.kernel.org/r/20220829181030.722891-1-ashok.raj@intel.com
---
 arch/x86/kernel/cpu/microcode/core.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index ad57e0e..6a41cee 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -491,7 +491,7 @@ wait_for_siblings:
  */
 static int microcode_reload_late(void)
 {
-	int ret;
+	int old = boot_cpu_data.microcode, ret;
 
 	pr_err("Attempting late microcode loading - it is dangerous and taints the kernel.\n");
 	pr_err("You should switch to early loading, if possible.\n");
@@ -503,7 +503,8 @@ static int microcode_reload_late(void)
 	if (ret == 0)
 		microcode_check();
 
-	pr_info("Reload completed, microcode revision: 0x%x\n", boot_cpu_data.microcode);
+	pr_info("Reload completed, microcode revision: 0x%x -> 0x%x\n",
+		old, boot_cpu_data.microcode);
 
 	return ret;
 }