linux-kernel - [PATCH 2/3] x86/microcode/intel: Perform a cache flush before ucode update.

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Date:   Wed, 21 Feb 2018 08:49:43 -0800
From:   Ashok Raj <ashok.raj@...el.com>
To:     bp@...e.de
Cc:     Ashok Raj <ashok.raj@...el.com>, X86 ML <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Tony Luck <tony.luck@...el.com>,
        Andi Kleen <andi.kleen@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Arjan Van De Ven <arjan.van.de.ven@...el.com>
Subject: [PATCH 2/3] x86/microcode/intel: Perform a cache flush before ucode update.

Microcode updates can be safer if the caches are clean.
Some of the issues around in certain Broadwell parts
can be addressed by doing a full cache flush.

Signed-off-by: Ashok Raj <ashok.raj@...el.com>
Cc: X86 ML <x86@...nel.org>
Cc: LKML <linux-kernel@...r.kernel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Tony Luck <tony.luck@...el.com>
Cc: Andi Kleen <andi.kleen@...el.com>
Cc: Boris Petkov <bp@...e.de>
Cc: Tom Lendacky <thomas.lendacky@....com>
Cc: Arjan Van De Ven <arjan.van.de.ven@...el.com>
---
 arch/x86/kernel/cpu/microcode/intel.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index eff80df..5d32724 100644
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -589,6 +589,7 @@ static int apply_microcode_early(struct ucode_cpu_info *uci, bool early)
 	if (!mc)
 		return 0;
 
+	wbinvd();
 	/* write microcode via MSR 0x79 */
 	native_wrmsrl(MSR_IA32_UCODE_WRITE, (unsigned long)mc->bits);
 
@@ -805,6 +806,7 @@ static enum ucode_state apply_microcode_intel(int cpu)
 		return UCODE_OK;
 	}
 
+	wbinvd();
 	/* write microcode via MSR 0x79 */
 	wrmsrl(MSR_IA32_UCODE_WRITE, (unsigned long)mc->bits);
 
-- 
2.7.4