[PATCH 01/11] x86: Use correct type for %cr4
[PATCH 02/11] x86: Merge fpu_init()
[PATCH 03/11] x86: Merge tolerant_fwait()
[PATCH 04/11] x86: Merge __save_init_fpu()
[PATCH 05/11] x86-64: Disable preemption when using TS_USEDFPU
[PATCH 06/11] x86-64: Fix %cs value in convert_from_fxsr()
[PATCH 07/11] x86-64: Simplify constraints for fxsave/fxtstor
[PATCH 08/11] x86-32: Remove math_emulate stub
[PATCH 09/11] x86: Merge fpu_save_init()
[PATCH 10/11] x86: Remove unnecessary ifdefs from i387 code.
[PATCH 11/11] x86: Remove PSHUFB_XMM5_* macros

 arch/x86/include/asm/i387.h      |  188 ++++++++++----------------------------
 arch/x86/include/asm/processor.h |    4 +-
 arch/x86/kernel/cpu/common.c     |    7 --
 arch/x86/kernel/i387.c           |   49 ++++------
 arch/x86/kernel/process_64.c     |    2 +-
 arch/x86/kernel/traps.c          |   35 +------
 6 files changed, 78 insertions(+), 207 deletions(-)

--

[ message continues ]

check_fpu() in bugs.c halts boot if no FPU is found and math emulation
isn't enabled.  Therefore this stub will never be used.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
---
 arch/x86/kernel/traps.c |   23 ++++++-----------------
 1 files changed, 6 insertions(+), 17 deletions(-)

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index d0029eb..d439685 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -776,21 +776,10 @@ asmlinkage void math_state_restore(void)
 }
 EXPORT_SYMBOL_GPL(math_state_restore);
 
-#ifndef CONFIG_MATH_EMULATION
-void math_emulate(struct math_emu_info *info)
-{
-	printk(KERN_EMERG
-		"math-emulation not enabled and no coprocessor found.\n");
-	printk(KERN_EMERG "killing %s.\n", current->comm);
-	force_sig(SIGFPE, current);
-	schedule();
-}
-#endif /* CONFIG_MATH_EMULATION */
-
 dotraplinkage void __kprobes
 do_device_not_available(struct pt_regs *regs, long error_code)
 {
-#ifdef CONFIG_X86_32
+#ifdef CONFIG_MATH_EMULATION
 	if (read_cr0() & X86_CR0_EM) {
 		struct math_emu_info info = { };
 
@@ -798,12 +787,12 @@ do_device_not_available(struct pt_regs *regs, long error_code)
 
 		info.regs = regs;
 		math_emulate(&info);
-	} else {
-		math_state_restore(); /* interrupts still off */
-		conditional_sti(regs);
+		return;
 	}
-#else
-	math_state_restore();
+#endif
+	math_state_restore(); /* interrupts still off */
+#ifdef CONFIG_X86_32
+	conditional_sti(regs);
 #endif
 }
 
-- 
1.7.2.2

--

[ message continues ]

Acked-by: Pekka Enberg <penberg@kernel.org>
--

[ message continues ]

Now that 32-bit can handle exceptions from the kernel, switch to using
the 64-bit version of tolerant_fwait() without fnclex.  In the unlikely
event an exception is triggered, it is simply ignored.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
---
 arch/x86/include/asm/i387.h |   19 ++++---------------
 1 files changed, 4 insertions(+), 15 deletions(-)

diff --git a/arch/x86/include/asm/i387.h b/arch/x86/include/asm/i387.h
index a73a8d5..5d8f9a7 100644
--- a/arch/x86/include/asm/i387.h
+++ b/arch/x86/include/asm/i387.h
@@ -77,15 +77,6 @@ static inline void sanitize_i387_state(struct task_struct *tsk)
 }
 
 #ifdef CONFIG_X86_64
-
-/* Ignore delayed exceptions from user space */
-static inline void tolerant_fwait(void)
-{
-	asm volatile("1: fwait\n"
-		     "2:\n"
-		     _ASM_EXTABLE(1b, 2b));
-}
-
 static inline int fxrstor_checking(struct i387_fxsave_struct *fx)
 {
 	int err;
@@ -220,11 +211,6 @@ extern void finit_soft_fpu(struct i387_soft_struct *soft);
 static inline void finit_soft_fpu(struct i387_soft_struct *soft) {}
 #endif
 
-static inline void tolerant_fwait(void)
-{
-	asm volatile("fnclex ; fwait");
-}
-
 /* perform fxrstor iff the processor has extended states, otherwise frstor */
 static inline int fxrstor_checking(struct i387_fxsave_struct *fx)
 {
@@ -344,7 +330,10 @@ static inline void __unlazy_fpu(struct task_struct *tsk)
 static inline void __clear_fpu(struct task_struct *tsk)
 {
 	if (task_thread_info(tsk)->status & TS_USEDFPU) {
-		tolerant_fwait();
+		/* Ignore delayed exceptions from user space */
+		asm volatile("1: fwait\n"
+			     "2:\n"
+			     _ASM_EXTABLE(1b, 2b));
 		task_thread_info(tsk)->status &= ~TS_USEDFPU;
 		stts();
 	}
-- 
1.7.2.2

--

[ message continues ]

Why is 32-bit able to handle exceptions? Is that part of this series
or is it some existing commit in tip or linus?
--

[ message continues ]

Commit e2e75c915de045f0785387dc32f55e92fab0614c merged the 32-bit and
64-bit math exception handlers into one, which calls
fixup_exception().

--
Brian Gerst
--

[ message continues ]

That could be in the changelog.

Acked-by: Pekka Enberg <penberg@kernel.org>
--

[ message continues ]