linux-kernel - [v2 11/13] x86/microcode/intel: Drop wbinvd() from microcode loading

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Message-Id: <20221103175901.164783-12-ashok.raj@intel.com>
Date:   Thu,  3 Nov 2022 17:58:59 +0000
From:   Ashok Raj <ashok.raj@...el.com>
To:     Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     "LKML Mailing List" <linux-kernel@...r.kernel.org>,
        X86-kernel <x86@...nel.org>, Tony Luck <tony.luck@...el.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Arjan van de Ven <arjan.van.de.ven@...el.com>,
        Andy Lutomirski <luto@...nel.org>,
        Jacon Jun Pan <jacob.jun.pan@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Kai Huang <kai.huang@...el.com>,
        Andrew Cooper <andrew.cooper3@...rix.com>,
        Ashok Raj <ashok.raj@...el.com>
Subject: [v2 11/13] 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 5d2ee76cd36c..7086670da606 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);
@@ -776,12 +771,6 @@ static enum ucode_state apply_microcode_intel(int cpu)
 	if (!prev_rev)
 		prev_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 */
 	wrmsrl(MSR_IA32_UCODE_WRITE, (unsigned long)mc->bits);
 
-- 
2.34.1