linux-kernel - Re: [tip: x86/pti] x86/speculation: Fix redundant MDS mitigation message

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Date:   Sat, 16 Nov 2019 15:24:11 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Waiman Long <longman@...hat.com>
Cc:     linux-tip-commits@...r.kernel.org,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Waiman Long <longman@...hat.com>, Borislav Petkov <bp@...e.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Mark Gross <mgross@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>,
        Tyler Hicks <tyhicks@...onical.com>, x86-ml <x86@...nel.org>,
        Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [tip: x86/pti] x86/speculation: Fix redundant MDS mitigation
 message

On Sat, Nov 16, 2019 at 12:25:19PM -0000, tip-bot2 for Waiman Long wrote:
> +static void __init mds_print_mitigation(void)
> +{
>  	pr_info("%s\n", mds_strings[mds_mitigation]);
>  }

Almost. This causes

MDS: Vulnerable

to be printed on an in-order 32-bit Atom here, which is wrong. I've
fixed it up to:

---
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index cb2fbd93ef4d..8bf64899f56a 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -256,6 +256,9 @@ static void __init mds_select_mitigation(void)
 
 static void __init mds_print_mitigation(void)
 {
+	if (!boot_cpu_has_bug(X86_BUG_MDS) || cpu_mitigations_off())
+		return;
+
 	pr_info("%s\n", mds_strings[mds_mitigation]);
 }
 

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette