linux-kernel - [PATCH 5/6] x86/bugs: Remove RFDS kernel parameter.

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Message-Id: <20240924223140.1054918-6-daniel.sneddon@linux.intel.com>
Date: Tue, 24 Sep 2024 15:31:39 -0700
From: Daniel Sneddon <daniel.sneddon@...ux.intel.com>
To: Jonathan Corbet <corbet@....net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Borislav Petkov <bp@...en8.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org
Cc: hpa@...or.com,
	linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	pawan.kumar.gupta@...ux.intel.com
Subject: [PATCH 5/6] x86/bugs: Remove RFDS kernel parameter.

Remove the reg_file_data_sampling kernel parameter since it can be set
using the common clear_cpu_buffers parameter.

Signed-off-by: Daniel Sneddon <daniel.sneddon@...ux.intel.com>
---
 .../admin-guide/kernel-parameters.txt         | 20 -------------------
 arch/x86/kernel/cpu/bugs.c                    | 17 ----------------
 2 files changed, 37 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 7afccd044fb8..2728fef51749 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1182,26 +1182,6 @@
 			The filter can be disabled or changed to another
 			driver later using sysfs.
 
-	reg_file_data_sampling=
-			[X86] Controls mitigation for Register File Data
-			Sampling (RFDS) vulnerability. RFDS is a CPU
-			vulnerability which may allow userspace to infer
-			kernel data values previously stored in floating point
-			registers, vector registers, or integer registers.
-			RFDS only affects Intel Atom processors.
-
-			on:	Turns ON the mitigation.
-			off:	Turns OFF the mitigation.
-
-			This parameter overrides the compile time default set
-			by CONFIG_MITIGATION_RFDS. Mitigation cannot be
-			disabled when other VERW based mitigations (like MDS)
-			are enabled. In order to disable RFDS mitigation all
-			VERW based mitigations need to be disabled.
-
-			For details see:
-			Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst
-
 	driver_async_probe=  [KNL]
 			List of driver names to be probed asynchronously. *
 			matches with all driver names. If * is specified, the
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 63a8cda2fe30..45411880481c 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -448,23 +448,6 @@ static void __init rfds_select_mitigation(void)
 		rfds_mitigation = RFDS_MITIGATION_UCODE_NEEDED;
 }
 
-static __init int rfds_parse_cmdline(char *str)
-{
-	if (!str)
-		return -EINVAL;
-
-	if (!boot_cpu_has_bug(X86_BUG_RFDS))
-		return 0;
-
-	if (!strcmp(str, "off"))
-		rfds_mitigation = RFDS_MITIGATION_OFF;
-	else if (!strcmp(str, "on"))
-		rfds_mitigation = RFDS_MITIGATION_VERW;
-
-	return 0;
-}
-early_param("reg_file_data_sampling", rfds_parse_cmdline);
-
 #undef pr_fmt
 #define pr_fmt(fmt)     "" fmt
 
-- 
2.25.1