Patch "x86/CPU: Check CPU feature bits after microcode upgrade" has been added to the 4.14-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    x86/CPU: Check CPU feature bits after microcode upgrade

to the 4.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     x86-cpu-check-cpu-feature-bits-after-microcode-upgrade.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 42ca8082e260dcfd8afa2afa6ec1940b9d41724c Mon Sep 17 00:00:00 2001
From: Borislav Petkov <bp@suse.de>
Date: Fri, 16 Feb 2018 12:26:40 +0100
Subject: x86/CPU: Check CPU feature bits after microcode upgrade

From: Borislav Petkov <bp@suse.de>

commit 42ca8082e260dcfd8afa2afa6ec1940b9d41724c upstream.

With some microcode upgrades, new CPUID features can become visible on
the CPU. Check what the kernel has mirrored now and issue a warning
hinting at possible things the user/admin can do to make use of the
newly visible features.

Originally-by: Ashok Raj <ashok.raj@intel.com>
Tested-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Ashok Raj <ashok.raj@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20180216112640.11554-4-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/x86/kernel/cpu/common.c |   20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1732,5 +1732,25 @@ core_initcall(init_cpu_syscore);
  */
 void microcode_check(void)
 {
+	struct cpuinfo_x86 info;
+
 	perf_check_microcode();
+
+	/* Reload CPUID max function as it might've changed. */
+	info.cpuid_level = cpuid_eax(0);
+
+	/*
+	 * Copy all capability leafs to pick up the synthetic ones so that
+	 * memcmp() below doesn't fail on that. The ones coming from CPUID will
+	 * get overwritten in get_cpu_cap().
+	 */
+	memcpy(&info.x86_capability, &boot_cpu_data.x86_capability, sizeof(info.x86_capability));
+
+	get_cpu_cap(&info);
+
+	if (!memcmp(&info.x86_capability, &boot_cpu_data.x86_capability, sizeof(info.x86_capability)))
+		return;
+
+	pr_warn("x86/CPU: CPU features have changed after loading microcode, but might not take effect.\n");
+	pr_warn("x86/CPU: Please consider either early loading through initrd/built-in or a potential BIOS update.\n");
 }


Patches currently in stable-queue which might be from bp@suse.de are

queue-4.14/x86-microcode-intel-check-microcode-revision-before-updating-sibling-threads.patch
queue-4.14/x86-microcode-attempt-late-loading-only-when-new-microcode-is-present.patch
queue-4.14/x86-microcode-propagate-return-value-from-updating-functions.patch
queue-4.14/x86-cpu-check-cpu-feature-bits-after-microcode-upgrade.patch
queue-4.14/x86-microcode-intel-writeback-and-invalidate-caches-before-updating-microcode.patch
queue-4.14/x86-microcode-intel-look-into-the-patch-cache-first.patch
queue-4.14/edac-mv64x60-fix-an-error-handling-path.patch
queue-4.14/x86-microcode-request-microcode-on-the-bsp.patch
queue-4.14/x86-microcode-get-rid-of-struct-apply_microcode_ctx.patch
queue-4.14/x86-microcode-fix-cpu-synchronization-routine.patch
queue-4.14/x86-microcode-synchronize-late-microcode-loading.patch
queue-4.14/x86-microcode-do-not-upload-microcode-if-cpus-are-offline.patch
queue-4.14/x86-cpu-add-a-microcode-loader-callback.patch