linux-kernel - [PATCH 4/6] x86/bugs: Remove MMIO kernel parameter

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Message-Id: <20240924223140.1054918-5-daniel.sneddon@linux.intel.com>
Date: Tue, 24 Sep 2024 15:31:38 -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 4/6] x86/bugs: Remove MMIO kernel parameter

Remove mmio_stale_data kernel parameter since it can be set with the common
clear_cpu_buffers parameter.

Signed-off-by: Daniel Sneddon <daniel.sneddon@...ux.intel.com>
---
 .../admin-guide/kernel-parameters.txt         | 34 -------------------
 arch/x86/kernel/cpu/bugs.c                    | 21 ------------
 2 files changed, 55 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 961e637b8126..7afccd044fb8 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3498,40 +3498,6 @@
 			log everything. Information is printed at KERN_DEBUG
 			so loglevel=8 may also need to be specified.
 
-	mmio_stale_data=
-			[X86,INTEL,EARLY] Control mitigation for the Processor
-			MMIO Stale Data vulnerabilities.
-
-			Processor MMIO Stale Data is a class of
-			vulnerabilities that may expose data after an MMIO
-			operation. Exposed data could originate or end in
-			the same CPU buffers as affected by MDS and TAA.
-			Therefore, similar to MDS and TAA, the mitigation
-			is to clear the affected CPU buffers.
-
-			This parameter controls the mitigation. The
-			options are:
-
-			full       - Enable mitigation on vulnerable CPUs
-
-			full,nosmt - Enable mitigation and disable SMT on
-				     vulnerable CPUs.
-
-			off        - Unconditionally disable mitigation
-
-			On MDS or TAA affected machines,
-			mmio_stale_data=off can be prevented by an active
-			MDS or TAA mitigation as these vulnerabilities are
-			mitigated with the same mechanism so in order to
-			disable this mitigation, you need to specify
-			mds=off and tsx_async_abort=off too.
-
-			Not specifying this option is equivalent to
-			mmio_stale_data=full.
-
-			For details see:
-			Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst
-
 	<module>.async_probe[=<bool>] [KNL]
 			If no <bool> value is specified or if the value
 			specified is not a valid <bool>, enable asynchronous
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 0a09f0d1a343..63a8cda2fe30 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -414,27 +414,6 @@ static void __init mmio_select_mitigation(void)
 		cpu_smt_disable(false);
 }
 
-static int __init mmio_stale_data_parse_cmdline(char *str)
-{
-	if (!boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA))
-		return 0;
-
-	if (!str)
-		return -EINVAL;
-
-	if (!strcmp(str, "off")) {
-		mmio_mitigation = MMIO_MITIGATION_OFF;
-	} else if (!strcmp(str, "full")) {
-		mmio_mitigation = MMIO_MITIGATION_VERW;
-	} else if (!strcmp(str, "full,nosmt")) {
-		mmio_mitigation = MMIO_MITIGATION_VERW;
-		mmio_nosmt = true;
-	}
-
-	return 0;
-}
-early_param("mmio_stale_data", mmio_stale_data_parse_cmdline);
-
 #undef pr_fmt
 #define pr_fmt(fmt)	"Register File Data Sampling: " fmt
 
-- 
2.25.1