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Date:   Thu, 18 Aug 2022 12:08:24 +0200
From:   Borislav Petkov <bp@alien8.de>
To:     Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Cc:     Jonathan Corbet <corbet@lwn.net>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
        "H. Peter Anvin" <hpa@zytor.com>, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, tony.luck@intel.com,
        antonio.gomez.iglesias@linux.intel.com,
        Daniel Sneddon <daniel.sneddon@linux.intel.com>,
        andrew.cooper3@citrix.com, Josh Poimboeuf <jpoimboe@kernel.org>
Subject: Re: [PATCH v2] x86/bugs: Add "unknown" reporting for MMIO Stale Data
Message-ID: <Yv4PmGS98IDZ7ujH@zn.tnic>
References: <79d2455c75bdbad4e68a3843fe1c1e67826008e6.1659562129.git.pawan.kumar.gupta@linux.intel.com>
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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