Commit 42ca8082 authored Feb 16, 2018 by Borislav Petkov Committed by Ingo Molnar Feb 17, 2018

x86/CPU: Check CPU feature bits after microcode upgrade



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>

parent 1008c52c

arch/x86/kernel/cpu/common.c

+20 −0

Original line number	Diff line number	Diff line
		@@ -1757,5 +1757,25 @@ 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");
		}

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