linux-kernel - [PATCH 10/13] x86/microcode/intel: Drop wbinvd() from microcode loading

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Date:   Fri, 14 Oct 2022 13:09:10 -0700
From:   Ashok Raj <ashok.raj@...el.com>
To:     Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     Tony Luck <tony.luck@...el.com>,
        Dave Hansen <dave.hansen@...el.com>,
        LKML Mailing List <linux-kernel@...r.kernel.org>,
        X86-kernel <x86@...nel.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        Arjan van de Ven <arjan.van.de.ven@...el.com>,
        Jacob Jun Pan <jacob.jun.pan@...el.com>,
        Ashok Raj <ashok.raj@...el.com>
Subject: [PATCH 10/13] x86/microcode/intel: Drop wbinvd() from microcode loading

Some older processors had a bad interaction when updating microcode if the
caches were dirty causing machine checks. The wbinvd() was added to
mitigate that before performing microcode updates. Now that Linux checks
for the minimum version before performing an update, those microcode
revisions can't be loaded. Remove calls to wbinvd().

Reviewed-by: Tony Luck <tony.luck@...el.com>
Signed-off-by: Ashok Raj <ashok.raj@...el.com>
---
 arch/x86/kernel/cpu/microcode/intel.c | 11 -----------
 1 file changed, 11 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index c8ee53fcf04d..c61aa661ac2f 100644
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -541,11 +541,6 @@ static int apply_microcode_early(struct ucode_cpu_info *uci, bool early)
 	}
 
 	old_rev = rev;
-	/*
-	 * Writeback and invalidate caches before updating microcode to avoid
-	 * internal issues depending on what the microcode is updating.
-	 */
-	native_wbinvd();
 
 	/* write microcode via MSR 0x79 */
 	native_wrmsrl(MSR_IA32_UCODE_WRITE, (unsigned long)mc->bits);
@@ -773,12 +768,6 @@ static enum ucode_state apply_microcode_intel(int cpu)
 		goto out;
 	}
 
-	/*
-	 * Writeback and invalidate caches before updating microcode to avoid
-	 * internal issues depending on what the microcode is updating.
-	 */
-	native_wbinvd();
-
 	/* write microcode via MSR 0x79 */
 	wrmsrl(MSR_IA32_UCODE_WRITE, (unsigned long)mc->bits);
 
-- 
2.34.1