[RFC PATCH 07/11] x86,fpu: store current fpu pointer, instead of fpu_owner_task

riel
2015-01-11T22:05:29Z

From: Rik van Riel <riel@redhat.com>

This change has no impact on normal tasks, but it allows tasks
with multiple FPU states(like a KVM vcpu thread) to check
whether its other FPU state is still loaded.

Exported so KVM can use it.

Signed-off-by: Rik van Riel <riel@redhat.com>
---
arch/x86/include/asm/fpu-internal.h | 15 ++++++++-------
arch/x86/kernel/cpu/common.c | 5 +++--
arch/x86/kernel/i387.c | 2 +-
3 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/arch/x86/include/asm/fpu-internal.h b/arch/x86/include/asm/fpu-internal.h
index a5a40c7..8546c0a 100644
--- a/arch/x86/include/asm/fpu-internal.h
+++ b/arch/x86/include/asm/fpu-internal.h
@@ -42,7 +42,7 @@ extern unsigned int mxcsr_feature_mask;
extern void fpu_init(void);
extern void eager_fpu_init(void);

-DECLARE_PER_CPU(struct task_struct *, fpu_owner_task);
+DECLARE_PER_CPU(struct fpu *, fpu_owner);

extern void convert_from_fxsr(struct user_i387_ia32_struct *env,
struct task_struct *tsk);
@@ -318,14 +318,14 @@ static inline int __thread_has_fpu(struct task_struct *tsk)
static inline void __thread_clear_has_fpu(struct task_struct *tsk)
{
tsk->thread.fpu.has_fpu = 0;
- this_cpu_write(fpu_owner_task, NULL);
+ this_cpu_write(fpu_owner, NULL);
}

/* Must be paired with a 'clts' before! */
static inline void __thread_set_has_fpu(struct task_struct *tsk)
{
tsk->thread.fpu.has_fpu = 1;
- this_cpu_write(fpu_owner_task, tsk);
+ this_cpu_write(fpu_owner, &tsk->thread.fpu);
}

/*
@@ -394,13 +394,14 @@ static inline void drop_init_fpu(struct task_struct *tsk)
*/
static inline void __cpu_disable_lazy_restore(unsigned int cpu)
{
- per_cpu(fpu_owner_task, cpu) = NULL;
+ per_cpu(fpu_owner, cpu) = NULL;
}

static inline int fpu_lazy_restore(struct task_struct *new, unsigned int cpu)
{
- return new == this_cpu_read_stable(fpu_owner_task) &&
- cpu == new->thread.fpu.last_cpu;
+ struct fpu *new_fpu = &new->thread.fpu;
+ return new_fpu == this_cpu_read_stable(fpu_owner) &&
+ cpu == new_fpu->last_cpu;
}

static inline void switch_fpu_prepare(struct task_struct *old, struct task_struct *new, int cpu)
@@ -421,7 +422,7 @@ static inline void switch_fpu_prepare(struct task_struct *old, struct task_struc
cpu = ~0;

old->thread.fpu.last_cpu = cpu;
- old->thread.fpu.has_fpu = 0; /* But leave fpu_owner_task! */
+ old->thread.fpu.has_fpu = 0; /* But leave fpu_owner! */

/* Don't change CR0.TS if we just switch! */
if (preload) {
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 36837bb..ad4d1a9 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1143,8 +1143,9 @@ DEFINE_PER_CPU(unsigned int, irq_count) __visible = -1;
DEFINE_PER_CPU(int, __preempt_count) = INIT_PREEMPT_COUNT;
EXPORT_PER_CPU_SYMBOL(__preempt_count);

-/* Task that currently has its FPU state loaded on the CPU. */
-DEFINE_PER_CPU(struct task_struct *, fpu_owner_task);
+/* FPU state that is currently loaded on the CPU. */
+DEFINE_PER_CPU(struct fpu *, fpu_owner);
+EXPORT_PER_CPU_SYMBOL_GPL(fpu_owner);

/*
* Special IST stacks which the CPU switches to when it calls
diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index a9a4229..c98f88d 100644
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -78,7 +78,7 @@ void __kernel_fpu_begin(void)
__save_init_fpu(me);
/* We do 'stts()' in __kernel_fpu_end() */
} else if (!use_eager_fpu()) {
- this_cpu_write(fpu_owner_task, NULL);
+ this_cpu_write(fpu_owner, NULL);
clts();
}
}
--
1.9.3