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

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Message-ID: <20180104185033.tsbijx32as6wqvye@pd.tnic>
Date:   Thu, 4 Jan 2018 19:50:33 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Andrea Arcangeli <aarcange@...hat.com>
Cc:     Tim Chen <tim.c.chen@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Arjan Van De Ven <arjan.van.de.ven@...el.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 7/7] x86/microcode: Recheck IBRS features on microcode
 reload

On Thu, Jan 04, 2018 at 07:34:30PM +0100, Andrea Arcangeli wrote:
> void spec_ctrl_rescan_cpuid(void)
> {
> 	int cpu;
> 
> 	if (use_ibp_disable)
> 		return;
> 	mutex_lock(&spec_ctrl_mutex);
> 	if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL ||
> 	    boot_cpu_data.x86_vendor == X86_VENDOR_AMD) {
> 		/* detect spec ctrl related cpuid additions */
> 		init_scattered_cpuid_features(&boot_cpu_data);

You don't need to noodle through all the scattered features - just the
two bits.

-- 
Regards/Gruss,
    Boris.

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