linux-kernel - Re: [PATCH v3 17/35] x86/bugs: Restructure l1tf mitigation

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Message-ID: <20250211012104.mxhmvghlmyf52uaa@jpoimboe>
Date: Mon, 10 Feb 2025 17:21:04 -0800
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: David Kaplan <david.kaplan@....com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
	Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	"H . Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 17/35] x86/bugs: Restructure l1tf mitigation

On Wed, Jan 08, 2025 at 02:24:57PM -0600, David Kaplan wrote:
>  static void __init l1tf_select_mitigation(void)
> +{
> +	if (!boot_cpu_has_bug(X86_BUG_L1TF) || cpu_mitigations_off()) {
> +		l1tf_mitigation = L1TF_MITIGATION_OFF;
> +		return;
> +	}
> +
> +	if (l1tf_mitigation == L1TF_MITIGATION_AUTO) {
> +		if (cpu_mitigations_auto_nosmt())
> +			l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOSMT;
> +		else
> +			l1tf_mitigation = L1TF_MITIGATION_FLUSH;
> +	}
> +
> +}

Extra whitespace.

> +
> +static void __init l1tf_apply_mitigation(void)
>  {
>  	u64 half_pa;
>  
>  	if (!boot_cpu_has_bug(X86_BUG_L1TF))
>  		return;
>  
> -	if (cpu_mitigations_off())
> -		l1tf_mitigation = L1TF_MITIGATION_OFF;
> -	else if (cpu_mitigations_auto_nosmt())
> -		l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOSMT;
> -
>  	override_cache_bits(&boot_cpu_data);
>  
>  	switch (l1tf_mitigation) {
>  	case L1TF_MITIGATION_OFF:
> +		return;

Note the PTE inverstion mitigation is already done unconditionally, the
X86_FEATURE_L1TF_PTEINV bit is just for reporting that.  So this
shouldn't return.

-- 
Josh