linux-kernel - Re: [PATCH v2] x86/bugs: Add "unknown" reporting for MMIO Stale Data

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Message-ID: <Yv4PmGS98IDZ7ujH@zn.tnic>
Date:   Thu, 18 Aug 2022 12:08:24 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
Cc:     Jonathan Corbet <corbet@....net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, tony.luck@...el.com,
        antonio.gomez.iglesias@...ux.intel.com,
        Daniel Sneddon <daniel.sneddon@...ux.intel.com>,
        andrew.cooper3@...rix.com, Josh Poimboeuf <jpoimboe@...nel.org>
Subject: Re: [PATCH v2] x86/bugs: Add "unknown" reporting for MMIO Stale Data

On Wed, Aug 03, 2022 at 02:41:32PM -0700, Pawan Gupta wrote:
> diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
> index 6761668100b9..fe3f7e762b80 100644
> --- a/arch/x86/kernel/cpu/bugs.c
> +++ b/arch/x86/kernel/cpu/bugs.c
> @@ -433,7 +433,8 @@ static void __init mmio_select_mitigation(void)
>  	u64 ia32_cap;
>  
>  	if (!boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA) ||
> -	    cpu_mitigations_off()) {
> +	     boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN) ||
> +	     cpu_mitigations_off()) {
>  		mmio_mitigation = MMIO_MITIGATION_OFF;
>  		return;
>  	}

Needs also:

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index d08c5589fa59..da7c361f47e0 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -539,6 +539,8 @@ static void __init md_clear_update_mitigation(void)
 		pr_info("TAA: %s\n", taa_strings[taa_mitigation]);
 	if (boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA))
 		pr_info("MMIO Stale Data: %s\n", mmio_strings[mmio_mitigation]);
+	else if (boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN))
+		pr_info("MMIO Stale Data: Unknown: No mitigations\n");
 }
 
 static void __init md_clear_select_mitigation(void)

I've added it.

-- 
Regards/Gruss,
    Boris.

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