linux-kernel - Re: [PATCH v5 04/16] x86/bugs: Restructure RFDS mitigation

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Message-ID: <20250427150903.GAaA5Ij3L6IHenvlMF@renoirsky.local>
Date: Sun, 27 Apr 2025 17:09:03 +0200
From: Borislav Petkov <bp@...en8.de>
To: David Kaplan <david.kaplan@....com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Josh Poimboeuf <jpoimboe@...nel.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 v5 04/16] x86/bugs: Restructure RFDS mitigation

On Fri, Apr 18, 2025 at 11:17:09AM -0500, David Kaplan wrote:
> +static bool __init rfds_has_ucode(void)
> +{
> +	return (x86_arch_cap_msr & ARCH_CAP_RFDS_CLEAR);
> +}

Might as well call it what the bit means and then the code reads a bit better:

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index e668ccccd8c7..2705105d9a5e 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -630,7 +630,7 @@ static const char * const rfds_strings[] = {
 	[RFDS_MITIGATION_UCODE_NEEDED]		= "Vulnerable: No microcode",
 };
 
-static bool __init rfds_has_ucode(void)
+static inline bool __init verw_clears_cpu_reg_file(void)
 {
 	return (x86_arch_cap_msr & ARCH_CAP_RFDS_CLEAR);
 }
@@ -648,7 +648,7 @@ static void __init rfds_select_mitigation(void)
 	if (rfds_mitigation == RFDS_MITIGATION_OFF)
 		return;
 
-	if (rfds_has_ucode())
+	if (verw_clears_cpu_reg_file())
 		verw_clear_cpu_buf_mitigation_selected = true;
 }
 
@@ -661,7 +661,7 @@ static void __init rfds_update_mitigation(void)
 		rfds_mitigation = RFDS_MITIGATION_VERW;
 
 	if (rfds_mitigation == RFDS_MITIGATION_VERW) {
-		if (!rfds_has_ucode())
+		if (!verw_clears_cpu_reg_file())
 			rfds_mitigation = RFDS_MITIGATION_UCODE_NEEDED;
 	}
 

-- 
Regards/Gruss,
    Boris.

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