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Darwish" , Andrew Cooper , Ard Biesheuvel , Arnd Bergmann , Borislav Petkov , Dave Hansen , "H . Peter Anvin" , John Ogness , Linus Torvalds , Peter Zijlstra , Thomas Gleixner , Arnd Bergmann Subject: [PATCH 08/15] x86/fpu: Remove MATH_EMULATION and related glue code Date: Thu, 15 May 2025 10:56:58 +0200 Message-ID: <20250515085708.2510123-9-mingo@kernel.org> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20250515085708.2510123-1-mingo@kernel.org> References: <20250515085708.2510123-1-mingo@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Signed-off-by: Ingo Molnar Reviewed-by: Arnd Bergmann Cc: Ahmed S . Darwish Cc: Andrew Cooper Cc: Ard Biesheuvel Cc: H . Peter Anvin Cc: John Ogness Cc: Linus Torvalds Cc: Peter Zijlstra Link: https://lore.kernel.org/r/20250425084216.3913608-9-mingo@kernel.org --- arch/x86/Kconfig | 27 --------------------------- arch/x86/Kconfig.cpufeatures | 1 - arch/x86/Makefile | 1 - arch/x86/include/asm/fpu/api.h | 6 ------ arch/x86/kernel/fpu/core.c | 5 ----- arch/x86/kernel/fpu/init.c | 9 +-------- arch/x86/kernel/traps.c | 14 -------------- 7 files changed, 1 insertion(+), 62 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 1f29dc81018f..e983705a4fe3 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -1637,33 +1637,6 @@ config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK Set whether the default state of memory_corruption_check is on or off. -config MATH_EMULATION - bool - depends on MODIFY_LDT_SYSCALL - prompt "Math emulation" if X86_32 && (M486SX || MELAN) - help - Linux can emulate a math coprocessor (used for floating point - operations) if you don't have one. 486DX and Pentium processors have - a math coprocessor built in, 486SX and 386 do not, unless you added - a 487DX or 387, respectively. (The messages during boot time can - give you some hints here ["man dmesg"].) Everyone needs either a - coprocessor or this emulation. - - If you don't have a math coprocessor, you need to say Y here; if you - say Y here even though you have a coprocessor, the coprocessor will - be used nevertheless. (This behavior can be changed with the kernel - command line option "no387", which comes handy if your coprocessor - is broken. Try "man bootparam" or see the documentation of your boot - loader (lilo or loadlin) about how to pass options to the kernel at - boot time.) This means that it is a good idea to say Y here if you - intend to use this kernel on different machines. - - More information about the internals of the Linux math coprocessor - emulation can be found in . - - If you are not sure, say Y; apart from resulting in a 66 KB bigger - kernel, it won't hurt. - config MTRR def_bool y prompt "MTRR (Memory Type Range Register) support" if EXPERT diff --git a/arch/x86/Kconfig.cpufeatures b/arch/x86/Kconfig.cpufeatures index e12d5b7e39a2..cd551818f451 100644 --- a/arch/x86/Kconfig.cpufeatures +++ b/arch/x86/Kconfig.cpufeatures @@ -66,7 +66,6 @@ config X86_REQUIRED_FEATURE_UP config X86_REQUIRED_FEATURE_FPU def_bool y - depends on !MATH_EMULATION config X86_REQUIRED_FEATURE_PAE def_bool y diff --git a/arch/x86/Makefile b/arch/x86/Makefile index 53daf4654f6c..84901c3acc94 100644 --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -285,7 +285,6 @@ core-y += arch/x86/boot/startup/ libs-y += arch/x86/lib/ # drivers-y are linked after core-y -drivers-$(CONFIG_MATH_EMULATION) += arch/x86/math-emu/ drivers-$(CONFIG_PCI) += arch/x86/pci/ # suspend and hibernation support diff --git a/arch/x86/include/asm/fpu/api.h b/arch/x86/include/asm/fpu/api.h index 8e6848f55dcd..87b794921070 100644 --- a/arch/x86/include/asm/fpu/api.h +++ b/arch/x86/include/asm/fpu/api.h @@ -119,12 +119,6 @@ extern void fpu__init_system(void); extern void fpu__init_check_bugs(void); extern void fpu__resume_cpu(void); -#ifdef CONFIG_MATH_EMULATION -extern void fpstate_init_soft(struct swregs_state *soft); -#else -static inline void fpstate_init_soft(struct swregs_state *soft) {} -#endif - /* State tracking */ DECLARE_PER_CPU(struct fpu *, fpu_fpregs_owner_ctx); diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index 948b4f5fad99..a39c0798c975 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -520,11 +520,6 @@ static inline void fpstate_init_fstate(struct fpstate *fpstate) */ void fpstate_init_user(struct fpstate *fpstate) { - if (!cpu_feature_enabled(X86_FEATURE_FPU)) { - fpstate_init_soft(&fpstate->regs.soft); - return; - } - xstate_init_xcomp_bv(&fpstate->regs.xsave, fpstate->xfeatures); if (cpu_feature_enabled(X86_FEATURE_FXSR)) diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c index 6bb3e35c40e2..20017fbfc16c 100644 --- a/arch/x86/kernel/fpu/init.c +++ b/arch/x86/kernel/fpu/init.c @@ -36,12 +36,7 @@ static void fpu__init_cpu_generic(void) write_cr0(cr0); /* Flush out any pending x87 state: */ -#ifdef CONFIG_MATH_EMULATION - if (!boot_cpu_has(X86_FEATURE_FPU)) - ; - else -#endif - asm volatile ("fninit"); + asm volatile ("fninit"); } /* @@ -83,13 +78,11 @@ static void __init fpu__init_system_early_generic(void) setup_clear_cpu_cap(X86_FEATURE_FPU); } -#ifndef CONFIG_MATH_EMULATION if (!test_cpu_cap(&boot_cpu_data, X86_FEATURE_FPU)) { pr_emerg("x86/fpu: Giving up, no FPU found and no math emulation present\n"); for (;;) asm volatile("hlt"); } -#endif } /* diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 8d08c58b3fe2..6b2ffb86c46d 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -1414,20 +1414,6 @@ DEFINE_IDTENTRY(exc_device_not_available) if (handle_xfd_event(regs)) return; -#ifdef CONFIG_MATH_EMULATION - if (!boot_cpu_has(X86_FEATURE_FPU) && (cr0 & X86_CR0_EM)) { - struct math_emu_info info = { }; - - cond_local_irq_enable(regs); - - info.regs = regs; - math_emulate(&info); - - cond_local_irq_disable(regs); - return; - } -#endif - /* This should not happen. */ if (WARN(cr0 & X86_CR0_TS, "CR0.TS was set")) { /* Try to fix it up and carry on. */ -- 2.45.2