linux-kernel - [Patch V1 1/7] x86/microcode/intel: Remove redundant microcode rev pr

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Message-Id: <20221129210832.107850-2-ashok.raj@intel.com>
Date:   Tue, 29 Nov 2022 13:08:26 -0800
From:   Ashok Raj <ashok.raj@...el.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     X86-kernel <x86@...nel.org>,
        LKML Mailing List <linux-kernel@...r.kernel.org>,
        Ashok Raj <ashok.raj@...el.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Tony Luck <tony.luck@...el.com>, alison.schofield@...el.com,
        reinette.chatre@...el.com
Subject: [Patch V1 1/7] x86/microcode/intel: Remove redundant microcode rev pr_info()s

There is a pr_info() to dump information about newly loaded microcode.
The code intends this pr_info() to be just once, but the check to ensure
is racy. Unfortunately this happens quite often in with this new change
resulting in multiple redundant prints on the console.

microcode_init()->schedule_on_each_cpu(setup_online_cpu)->collect_cpu_info

[   33.688639] microcode: sig=0x50654, pf=0x80, revision=0x2006e05
[   33.688659] microcode: sig=0x50654, pf=0x80, revision=0x2006e05
[   33.688660] microcode: sig=0x50654, pf=0x80, revision=0x2006e05

There is already a pr_info() in microcode/core.c as shown below:

microcode: Reload completed, microcode revision: 0x2b000041 -> 0x2b000070

The sig and pf aren't that useful to end user, they are available via
/proc/cpuinfo and this never changes between microcode loads.

Remove the redundant pr_info() and the racy single print checks. This
removes the race entirely, zap the duplicated pr_info() spam and
simplify the code.

Fixes: b6f86689d5b7 ("x86/microcode: Rip out the subsys interface gunk")
Reported-by: Tony Luck <tony.luck@...el.com>
Signed-off-by: Ashok Raj <ashok.raj@...el.com>
---
 arch/x86/kernel/cpu/microcode/intel.c | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index c4a00fb97f61..4f93875f57b4 100644
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -554,7 +554,6 @@ void reload_ucode_intel(void)
 
 static int collect_cpu_info(int cpu_num, struct cpu_signature *csig)
 {
-	static struct cpu_signature prev;
 	struct cpuinfo_x86 *c = &cpu_data(cpu_num);
 	unsigned int val[2];
 
@@ -570,13 +569,6 @@ static int collect_cpu_info(int cpu_num, struct cpu_signature *csig)
 
 	csig->rev = c->microcode;
 
-	/* No extra locking on prev, races are harmless. */
-	if (csig->sig != prev.sig || csig->pf != prev.pf || csig->rev != prev.rev) {
-		pr_info("sig=0x%x, pf=0x%x, revision=0x%x\n",
-			csig->sig, csig->pf, csig->rev);
-		prev = *csig;
-	}
-
 	return 0;
 }
 
-- 
2.34.1