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Message-ID: <alpine.LFD.2.02.1202211339590.5354@i5.linux-foundation.org>
Date: Tue, 21 Feb 2012 13:40:24 -0800 (PST)
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: "H. Peter Anvin" <hpa@...or.com>
cc: Josh Boyer <jwboyer@...il.com>,
Jongman Heo <jongman.heo@...sung.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH 1/2] i387: uninline the generic FP helpers that we expose to
kernel modules
From: Linus Torvalds <torvalds@...ux-foundation.org>
Date: Tue, 21 Feb 2012 10:25:45 -0800
Subject: [PATCH 1/2] i387: uninline the generic FP helpers that we expose to kernel modules
Instead of exporting the very low-level internals of the FPU state
save/restore code (ie things like 'fpu_owner_task'), we should export
the higher-level interfaces.
Inlining these things is pointless anyway: sure, sometimes the end
result is small, but while 'stts()' can result in just three x86
instructions, those are not cheap instructions (writing %cr0 is a
serializing instruction and a very slow one at that).
So the overhead of a function call is not noticeable, and we really
don't want random modules mucking about with our internal state save
logic anyway.
So this unexports 'fpu_owner_task', and instead uninlines and exports
the actual functions that modules can use: fpu_kernel_begin/end() and
unlazy_fpu().
Acked-by: H. Peter Anvin <hpa@...or.com>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
---
This is the same patch I already sent out earlier, now with a commit
message and Peter's ack added.
arch/x86/include/asm/i387.h | 78 ++--------------------------------------
arch/x86/kernel/cpu/common.c | 2 -
arch/x86/kernel/i387.c | 80 ++++++++++++++++++++++++++++++++++++++++++
3 files changed, 84 insertions(+), 76 deletions(-)
diff --git a/arch/x86/include/asm/i387.h b/arch/x86/include/asm/i387.h
index 247904945d3f..0c1031d354f2 100644
--- a/arch/x86/include/asm/i387.h
+++ b/arch/x86/include/asm/i387.h
@@ -419,70 +419,9 @@ static inline void __clear_fpu(struct task_struct *tsk)
}
}
-/*
- * Were we in an interrupt that interrupted kernel mode?
- *
- * We can do a kernel_fpu_begin/end() pair *ONLY* if that
- * pair does nothing at all: the thread must not have fpu (so
- * that we don't try to save the FPU state), and TS must
- * be set (so that the clts/stts pair does nothing that is
- * visible in the interrupted kernel thread).
- */
-static inline bool interrupted_kernel_fpu_idle(void)
-{
- return !__thread_has_fpu(current) &&
- (read_cr0() & X86_CR0_TS);
-}
-
-/*
- * Were we in user mode (or vm86 mode) when we were
- * interrupted?
- *
- * Doing kernel_fpu_begin/end() is ok if we are running
- * in an interrupt context from user mode - we'll just
- * save the FPU state as required.
- */
-static inline bool interrupted_user_mode(void)
-{
- struct pt_regs *regs = get_irq_regs();
- return regs && user_mode_vm(regs);
-}
-
-/*
- * Can we use the FPU in kernel mode with the
- * whole "kernel_fpu_begin/end()" sequence?
- *
- * It's always ok in process context (ie "not interrupt")
- * but it is sometimes ok even from an irq.
- */
-static inline bool irq_fpu_usable(void)
-{
- return !in_interrupt() ||
- interrupted_user_mode() ||
- interrupted_kernel_fpu_idle();
-}
-
-static inline void kernel_fpu_begin(void)
-{
- struct task_struct *me = current;
-
- WARN_ON_ONCE(!irq_fpu_usable());
- preempt_disable();
- if (__thread_has_fpu(me)) {
- __save_init_fpu(me);
- __thread_clear_has_fpu(me);
- /* We do 'stts()' in kernel_fpu_end() */
- } else {
- percpu_write(fpu_owner_task, NULL);
- clts();
- }
-}
-
-static inline void kernel_fpu_end(void)
-{
- stts();
- preempt_enable();
-}
+extern bool irq_fpu_usable(void);
+extern void kernel_fpu_begin(void);
+extern void kernel_fpu_end(void);
/*
* Some instructions like VIA's padlock instructions generate a spurious
@@ -566,16 +505,7 @@ static inline void save_init_fpu(struct task_struct *tsk)
preempt_enable();
}
-static inline void unlazy_fpu(struct task_struct *tsk)
-{
- preempt_disable();
- if (__thread_has_fpu(tsk)) {
- __save_init_fpu(tsk);
- __thread_fpu_end(tsk);
- } else
- tsk->fpu_counter = 0;
- preempt_enable();
-}
+extern void unlazy_fpu(struct task_struct *tsk);
static inline void clear_fpu(struct task_struct *tsk)
{
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index c0f7d68d318f..cb71b01ab66e 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1045,7 +1045,6 @@ DEFINE_PER_CPU(char *, irq_stack_ptr) =
DEFINE_PER_CPU(unsigned int, irq_count) = -1;
DEFINE_PER_CPU(struct task_struct *, fpu_owner_task);
-EXPORT_PER_CPU_SYMBOL(fpu_owner_task);
/*
* Special IST stacks which the CPU switches to when it calls
@@ -1115,7 +1114,6 @@ void debug_stack_reset(void)
DEFINE_PER_CPU(struct task_struct *, current_task) = &init_task;
EXPORT_PER_CPU_SYMBOL(current_task);
DEFINE_PER_CPU(struct task_struct *, fpu_owner_task);
-EXPORT_PER_CPU_SYMBOL(fpu_owner_task);
#ifdef CONFIG_CC_STACKPROTECTOR
DEFINE_PER_CPU_ALIGNED(struct stack_canary, stack_canary);
diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index 739d8598f789..17b7549c4134 100644
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -32,6 +32,86 @@
# define user32_fxsr_struct user_fxsr_struct
#endif
+/*
+ * Were we in an interrupt that interrupted kernel mode?
+ *
+ * We can do a kernel_fpu_begin/end() pair *ONLY* if that
+ * pair does nothing at all: the thread must not have fpu (so
+ * that we don't try to save the FPU state), and TS must
+ * be set (so that the clts/stts pair does nothing that is
+ * visible in the interrupted kernel thread).
+ */
+static inline bool interrupted_kernel_fpu_idle(void)
+{
+ return !__thread_has_fpu(current) &&
+ (read_cr0() & X86_CR0_TS);
+}
+
+/*
+ * Were we in user mode (or vm86 mode) when we were
+ * interrupted?
+ *
+ * Doing kernel_fpu_begin/end() is ok if we are running
+ * in an interrupt context from user mode - we'll just
+ * save the FPU state as required.
+ */
+static inline bool interrupted_user_mode(void)
+{
+ struct pt_regs *regs = get_irq_regs();
+ return regs && user_mode_vm(regs);
+}
+
+/*
+ * Can we use the FPU in kernel mode with the
+ * whole "kernel_fpu_begin/end()" sequence?
+ *
+ * It's always ok in process context (ie "not interrupt")
+ * but it is sometimes ok even from an irq.
+ */
+bool irq_fpu_usable(void)
+{
+ return !in_interrupt() ||
+ interrupted_user_mode() ||
+ interrupted_kernel_fpu_idle();
+}
+EXPORT_SYMBOL(irq_fpu_usable);
+
+void kernel_fpu_begin(void)
+{
+ struct task_struct *me = current;
+
+ WARN_ON_ONCE(!irq_fpu_usable());
+ preempt_disable();
+ if (__thread_has_fpu(me)) {
+ __save_init_fpu(me);
+ __thread_clear_has_fpu(me);
+ /* We do 'stts()' in kernel_fpu_end() */
+ } else {
+ percpu_write(fpu_owner_task, NULL);
+ clts();
+ }
+}
+EXPORT_SYMBOL(kernel_fpu_begin);
+
+void kernel_fpu_end(void)
+{
+ stts();
+ preempt_enable();
+}
+EXPORT_SYMBOL(kernel_fpu_end);
+
+void unlazy_fpu(struct task_struct *tsk)
+{
+ preempt_disable();
+ if (__thread_has_fpu(tsk)) {
+ __save_init_fpu(tsk);
+ __thread_fpu_end(tsk);
+ } else
+ tsk->fpu_counter = 0;
+ preempt_enable();
+}
+EXPORT_SYMBOL(unlazy_fpu);
+
#ifdef CONFIG_MATH_EMULATION
# define HAVE_HWFP (boot_cpu_data.hard_math)
#else
--
1.7.9.188.g12766.dirty
--
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