linux-kernel - [PATCH 7/7] x86/microcode: Recheck IBRS features on microcode reload

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Date:   Thu,  4 Jan 2018 09:56:48 -0800
From:   Tim Chen <tim.c.chen@...ux.intel.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg KH <gregkh@...uxfoundation.org>
Cc:     Tim Chen <tim.c.chen@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Arjan Van De Ven <arjan.van.de.ven@...el.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 7/7] x86/microcode: Recheck IBRS features on microcode reload

On new microcode write, check whether IBRS
is present by rescanning scattered CPU features.

Signed-off-by: Tim Chen <tim.c.chen@...ux.intel.com>
---
 arch/x86/kernel/cpu/microcode/core.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index c4fa4a8..44b9355 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -40,6 +40,7 @@
 #include <asm/processor.h>
 #include <asm/cmdline.h>
 #include <asm/setup.h>
+#include <asm/spec_ctrl.h>
 
 #define DRIVER_VERSION	"2.2"
 
@@ -444,6 +445,11 @@ static ssize_t microcode_write(struct file *file, const char __user *buf,
 	if (ret > 0)
 		perf_check_microcode();
 
+	/* check spec_ctrl capabilities */
+	mutex_lock(&spec_ctrl_mutex);
+	init_scattered_cpuid_features(&boot_cpu_data);
+	mutex_unlock(&spec_ctrl_mutex);
+
 	mutex_unlock(&microcode_mutex);
 	put_online_cpus();
 
-- 
2.9.4