linux-kernel - [PATCH 09/15] x86/fpu: Remove the 'no387' boot option

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Message-ID: <20250425084216.3913608-10-mingo@kernel.org>
Date: Fri, 25 Apr 2025 10:42:06 +0200
From: Ingo Molnar <mingo@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: Ingo Molnar <mingo@...nel.org>,
	"Ahmed S . Darwish" <darwi@...utronix.de>,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	Ard Biesheuvel <ardb@...nel.org>,
	Arnd Bergmann <arnd@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H . Peter Anvin" <hpa@...or.com>,
	John Ogness <john.ogness@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 09/15] x86/fpu: Remove the 'no387' boot option

Without math emulation there's no point to this option.

Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 Documentation/admin-guide/kernel-parameters.txt |  4 ----
 arch/x86/Kconfig                                | 20 +++++++++-----------
 arch/x86/kernel/cpu/common.c                    |  7 -------
 3 files changed, 9 insertions(+), 22 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index d9fd26b95b34..6d391d76336f 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4049,10 +4049,6 @@
 			These settings can be accessed at runtime via
 			the nmi_watchdog and hardlockup_panic sysctls.
 
-	no387		[BUGS=X86-32] Tells the kernel to use the 387 maths
-			emulation library even if a 387 maths coprocessor
-			is present.
-
 	no4lvl		[RISCV,EARLY] Disable 4-level and 5-level paging modes.
 			Forces kernel to use 3-level paging instead.
 
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index cd9dd10b15d2..137b5ddf1f86 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2725,18 +2725,16 @@ menuconfig APM
 	  1) make sure that you have enough swap space and that it is
 	  enabled.
 	  2) pass the "idle=poll" option to the kernel
-	  3) switch on floating point emulation in the kernel and pass
-	  the "no387" option to the kernel
-	  4) pass the "floppy=nodma" option to the kernel
-	  5) pass the "mem=4M" option to the kernel (thereby disabling
+	  3) pass the "floppy=nodma" option to the kernel
+	  4) pass the "mem=4M" option to the kernel (thereby disabling
 	  all but the first 4 MB of RAM)
-	  6) make sure that the CPU is not over clocked.
-	  7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
-	  8) disable the cache from your BIOS settings
-	  9) install a fan for the video card or exchange video RAM
-	  10) install a better fan for the CPU
-	  11) exchange RAM chips
-	  12) exchange the motherboard.
+	  5) make sure that the CPU is not over clocked.
+	  6) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
+	  7) disable the cache from your BIOS settings
+	  8) install a fan for the video card or exchange video RAM
+	  9) install a better fan for the CPU
+	  10) exchange RAM chips
+	  11) exchange the motherboard.
 
 	  To compile this driver as a module, choose M here: the
 	  module will be called apm.
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 12126adbc3a9..1755ef511fd7 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1574,13 +1574,6 @@ static void __init cpu_parse_early_param(void)
 	int arglen;
 
 #ifdef CONFIG_X86_32
-	if (cmdline_find_option_bool(boot_command_line, "no387"))
-#ifdef CONFIG_MATH_EMULATION
-		setup_clear_cpu_cap(X86_FEATURE_FPU);
-#else
-		pr_err("Option 'no387' required CONFIG_MATH_EMULATION enabled.\n");
-#endif
-
 	if (cmdline_find_option_bool(boot_command_line, "nofxsr"))
 		setup_clear_cpu_cap(X86_FEATURE_FXSR);
 #endif
-- 
2.45.2