[v2 2/3] x86/microcode/intel: Perform a cache flush before ucode update.

[Ashok Raj]

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@xxxxxxxxx>
Cc: X86 ML <x86@xxxxxxxxxx>
Cc: LKML <linux-kernel@xxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Cc: Andi Kleen <andi.kleen@xxxxxxxxx>
Cc: Boris Petkov <bp@xxxxxxx>
Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
Cc: Arjan Van De Ven <arjan.van.de.ven@xxxxxxxxx>
---
 arch/x86/kernel/cpu/microcode/intel.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index 137c9f5..50e48c4 100644
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -601,6 +601,13 @@ static int apply_microcode_early(struct ucode_cpu_info *uci, bool early)
 		return UCODE_OK;
 	}
 
+	/*
+	 * 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.
+	 */
+	native_wbinvd();
+
 	/* write microcode via MSR 0x79 */
 	native_wrmsrl(MSR_IA32_UCODE_WRITE, (unsigned long)mc->bits);
 
@@ -817,6 +824,13 @@ static enum ucode_state apply_microcode_intel(int cpu)
 		return UCODE_OK;
 	}
 
+	/*
+	 * 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.
+	 */
+	wbinvd();
+
 	/* write microcode via MSR 0x79 */
 	wrmsrl(MSR_IA32_UCODE_WRITE, (unsigned long)mc->bits);
 
-- 
2.7.4