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Message-ID: <20250425084216.3913608-9-mingo@kernel.org>
Date: Fri, 25 Apr 2025 10:42:05 +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 08/15] x86/fpu: Remove MATH_EMULATION and related glue code
Signed-off-by: Ingo Molnar <mingo@...nel.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 62a9db3efa93..cd9dd10b15d2 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1636,33 +1636,6 @@ 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 <file:arch/x86/math-emu/README>.
-
- 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 594723005d95..15975f63952e 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -284,7 +284,6 @@ archprepare: $(cpufeaturemasks.hdr)
libs-y += arch/x86/lib/
# drivers-y are linked after core-y
-drivers-$(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 f42de5f05e7e..def9f7261b0d 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 91d6341f281f..59a4f430b46e 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -512,11 +512,6 @@ 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 998a08f17e33..7f64d0677160 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))
- fpstate_init_soft(¤t->thread.fpu.fpstate->regs.soft);
- else
-#endif
- asm volatile ("fninit");
+ asm volatile ("fninit");
}
/*
@@ -81,13 +76,11 @@ 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 8d5bbac04435..6467b7832fea 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -1413,20 +1413,6 @@ 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
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