linux-kernel - [PATCH 3/6] x86/bugs: Remove TAA kernel parameter.

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Message-Id: <20240924223140.1054918-4-daniel.sneddon@linux.intel.com>
Date: Tue, 24 Sep 2024 15:31:37 -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 3/6] x86/bugs: Remove TAA kernel parameter.

Remove tsx_async_abort kernel parameter since it can be set with the common
clar_cpu_buffers parameter.

Signed-off-by: Daniel Sneddon <daniel.sneddon@...ux.intel.com>
---
 .../admin-guide/kernel-parameters.txt         | 41 -------------------
 arch/x86/kernel/cpu/bugs.c                    | 21 ----------
 2 files changed, 62 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 2753a1e51da5..961e637b8126 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -6883,47 +6883,6 @@
 			See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
 			for more details.
 
-	tsx_async_abort= [X86,INTEL,EARLY] Control mitigation for the TSX Async
-			Abort (TAA) vulnerability.
-
-			Similar to Micro-architectural Data Sampling (MDS)
-			certain CPUs that support Transactional
-			Synchronization Extensions (TSX) are vulnerable to an
-			exploit against CPU internal buffers which can forward
-			information to a disclosure gadget under certain
-			conditions.
-
-			In vulnerable processors, the speculatively forwarded
-			data can be used in a cache side channel attack, to
-			access data to which the attacker does not have direct
-			access.
-
-			This parameter controls the TAA mitigation.  The
-			options are:
-
-			full       - Enable TAA mitigation on vulnerable CPUs
-				     if TSX is enabled.
-
-			full,nosmt - Enable TAA mitigation and disable SMT on
-				     vulnerable CPUs. If TSX is disabled, SMT
-				     is not disabled because CPU is not
-				     vulnerable to cross-thread TAA attacks.
-			off        - Unconditionally disable TAA mitigation
-
-			On MDS-affected machines, tsx_async_abort=off can be
-			prevented by an active MDS mitigation as both vulnerabilities
-			are mitigated with the same mechanism so in order to disable
-			this mitigation, you need to specify mds=off too.
-
-			Not specifying this option is equivalent to
-			tsx_async_abort=full.  On CPUs which are MDS affected
-			and deploy MDS mitigation, TAA mitigation is not
-			required and doesn't provide any additional
-			mitigation.
-
-			For details see:
-			Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
-
 	turbografx.map[2|3]=	[HW,JOY]
 			TurboGraFX parallel port interface
 			Format:
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index ed5524bc3ee4..0a09f0d1a343 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -339,27 +339,6 @@ static void __init taa_select_mitigation(void)
 		cpu_smt_disable(false);
 }
 
-static int __init tsx_async_abort_parse_cmdline(char *str)
-{
-	if (!boot_cpu_has_bug(X86_BUG_TAA))
-		return 0;
-
-	if (!str)
-		return -EINVAL;
-
-	if (!strcmp(str, "off")) {
-		taa_mitigation = TAA_MITIGATION_OFF;
-	} else if (!strcmp(str, "full")) {
-		taa_mitigation = TAA_MITIGATION_VERW;
-	} else if (!strcmp(str, "full,nosmt")) {
-		taa_mitigation = TAA_MITIGATION_VERW;
-		taa_nosmt = true;
-	}
-
-	return 0;
-}
-early_param("tsx_async_abort", tsx_async_abort_parse_cmdline);
-
 #undef pr_fmt
 #define pr_fmt(fmt)	"MMIO Stale Data: " fmt
 
-- 
2.25.1