linux-kernel - Re: [PATCH 3/5] x86, AMD: cleanup: merge common code in early microcode loading

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Date:	Thu, 8 Aug 2013 20:28:53 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	"Yu, Fenghua" <fenghua.yu@...el.com>,
	Torsten Kaiser <just.for.lkml@...glemail.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Jacob Shin <jacob.shin@....com>,
	Johannes Hirte <johannes.hirte@....tu-ilmenau.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/5] x86, AMD: cleanup: merge common code in early
 microcode loading

On Thu, Aug 08, 2013 at 12:02:38PM +0200, Borislav Petkov wrote:
> On Wed, Aug 07, 2013 at 07:22:39PM -0700, H. Peter Anvin wrote:
> > How much does this matter?
> 
> I know what you're asking :-)
> 
> And no, it doesn't really matter as we fail in the patch version check
> so maybe only a comment will suffice here so that people don't get
> confused.

IOW, something like that:

---
From: Borislav Petkov <bp@...e.de>
Date: Thu, 8 Aug 2013 20:26:24 +0200
Subject: [PATCH] x86, microcode: Clarify loading on the AP

Hold it down why we're calling the AP microcode loading routine on the
BSP too, for future reference.

Signed-off-by: Borislav Petkov <bp@...e.de>
---
 arch/x86/kernel/cpu/common.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 25eb2747b063..58d37a27d317 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1226,8 +1226,12 @@ void cpu_init(void)
 	int i;
 
 	/*
-	 * Load microcode on this cpu if a valid microcode is available.
-	 * This is early microcode loading procedure.
+	 * Load microcode on this cpu if a valid microcode is available. This
+	 * is early microcode loading procedure. We execute this on the BSP too
+	 * but since a microcode has been potentially already applied on the
+	 * BSP, we will return prematurely here. It is easier to simply call it
+	 * again than filtering all the possible cases when we're not running
+	 * on the BSP.
 	 */
 	load_ucode_ap();
 
-- 
1.8.3

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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