linux-kernel - [4.15 & 4.14 stable 06/12] x86/microcode/intel: Writeback and invalidate caches before updating microcode

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Message-Id: <1523039426-3938-7-git-send-email-ashok.raj@intel.com>
Date:   Fri,  6 Apr 2018 11:30:20 -0700
From:   Ashok Raj <ashok.raj@...el.com>
To:     gregkh@...uxfoundation.org, tglx@...utronix.de
Cc:     Ashok Raj <ashok.raj@...el.com>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, bp@...e.de, thomas.lendacky@....com,
        arjan.van.de.ven@...el.com, asit.k.mallick@...el.com
Subject: [4.15 & 4.14 stable 06/12] x86/microcode/intel: Writeback and invalidate caches before updating microcode

commit 91df9fdf51492aec9fed6b4cbd33160886740f47 upstream

Updating microcode is less error prone when caches have been flushed and
depending on what exactly the microcode is updating. For example, some
of the issues around certain Broadwell parts can be addressed by doing a
full cache flush.

[ Borislav: Massage it and use native_wbinvd() in both cases. ]

Signed-off-by: Ashok Raj <ashok.raj@...el.com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Tested-by: Tom Lendacky <thomas.lendacky@....com>
Tested-by: Ashok Raj <ashok.raj@...el.com>
Cc: Arjan Van De Ven <arjan.van.de.ven@...el.com>
Cc: Tom Lendacky <thomas.lendacky@....com>
Cc: Asit K Mallick <asit.k.mallick@...el.com>
Cc: stable@...r.kernel.org
Link: http://lkml.kernel.org/r/1519352533-15992-3-git-send-email-ashok.raj@intel.com
Link: https://lkml.kernel.org/r/20180228102846.13447-4-bp@alien8.de
---
 arch/x86/kernel/cpu/microcode/intel.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index 87bd6dc..e2864bc 100644
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -600,6 +600,12 @@ static int apply_microcode_early(struct ucode_cpu_info *uci, bool early)
 		return UCODE_OK;
 	}
 
+	/*
+	 * 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);
 
@@ -816,6 +822,12 @@ static enum ucode_state apply_microcode_intel(int cpu)
 		return UCODE_OK;
 	}
 
+	/*
+	 * 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);
 
-- 
2.7.4