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x86, fpu: decouple non-lazy/eager fpu restore from xsave

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Decouple non-lazy/eager fpu restore policy from the existence of the xsave
feature. Introduce a synthetic CPUID flag to represent the eagerfpu
policy. "eagerfpu=on" boot paramter will enable the policy.

Requested-by: H. Peter Anvin <hpa@zytor.com>
Requested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Link: http://lkml.kernel.org/r/1347300665-6209-2-git-send-email-suresh.b.siddha@intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
This commit is contained in:
Suresh Siddha
2012-09-06 14:58:52 -07:00
committed by H. Peter Anvin
parent 304bceda6a
commit 5d2bd7009f
8 changed files with 112 additions and 66 deletions
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54
arch/x86/include/asm/fpu-internal.h
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@@ -38,6 +38,7 @@ int ia32_setup_frame(int sig, struct k_sigaction *ka,
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);
@@ -84,6 +85,11 @@ static inline int is_x32_frame(void)
#define X87_FSW_ES (1 << 7) /* Exception Summary */
static __always_inline __pure bool use_eager_fpu(void)
{
return static_cpu_has(X86_FEATURE_EAGER_FPU);
}
static __always_inline __pure bool use_xsaveopt(void)
{
return static_cpu_has(X86_FEATURE_XSAVEOPT);
@@ -99,6 +105,14 @@ static __always_inline __pure bool use_fxsr(void)
return static_cpu_has(X86_FEATURE_FXSR);
}
static inline void fx_finit(struct i387_fxsave_struct *fx)
{
memset(fx, 0, xstate_size);
fx->cwd = 0x37f;
if (cpu_has_xmm)
fx->mxcsr = MXCSR_DEFAULT;
}
extern void __sanitize_i387_state(struct task_struct *);
static inline void sanitize_i387_state(struct task_struct *tsk)
@@ -291,13 +305,13 @@ static inline void __thread_set_has_fpu(struct task_struct *tsk)
static inline void __thread_fpu_end(struct task_struct *tsk)
{
__thread_clear_has_fpu(tsk);
if (!use_xsave())
if (!use_eager_fpu())
stts();
}
static inline void __thread_fpu_begin(struct task_struct *tsk)
{
if (!use_xsave())
if (!use_eager_fpu())
clts();
__thread_set_has_fpu(tsk);
}
@@ -327,10 +341,14 @@ static inline void drop_fpu(struct task_struct *tsk)
static inline void drop_init_fpu(struct task_struct *tsk)
{
if (!use_xsave())
if (!use_eager_fpu())
drop_fpu(tsk);
else
xrstor_state(init_xstate_buf, -1);
else {
if (use_xsave())
xrstor_state(init_xstate_buf, -1);
else
fxrstor_checking(&init_xstate_buf->i387);
}
}
/*
@@ -370,7 +388,7 @@ static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct ta
* If the task has used the math, pre-load the FPU on xsave processors
* or if the past 5 consecutive context-switches used math.
*/
fpu.preload = tsk_used_math(new) && (use_xsave() ||
fpu.preload = tsk_used_math(new) && (use_eager_fpu() ||
new->fpu_counter > 5);
if (__thread_has_fpu(old)) {
if (!__save_init_fpu(old))
@@ -383,14 +401,14 @@ static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct ta
new->fpu_counter++;
__thread_set_has_fpu(new);
prefetch(new->thread.fpu.state);
} else if (!use_xsave())
} else if (!use_eager_fpu())
stts();
} else {
old->fpu_counter = 0;
old->thread.fpu.last_cpu = ~0;
if (fpu.preload) {
new->fpu_counter++;
if (!use_xsave() && fpu_lazy_restore(new, cpu))
if (!use_eager_fpu() && fpu_lazy_restore(new, cpu))
fpu.preload = 0;
else
prefetch(new->thread.fpu.state);
@@ -452,6 +470,14 @@ static inline void user_fpu_begin(void)
preempt_enable();
}
static inline void __save_fpu(struct task_struct *tsk)
{
if (use_xsave())
xsave_state(&tsk->thread.fpu.state->xsave, -1);
else
fpu_fxsave(&tsk->thread.fpu);
}
/*
* These disable preemption on their own and are safe
*/
@@ -459,8 +485,8 @@ static inline void save_init_fpu(struct task_struct *tsk)
{
WARN_ON_ONCE(!__thread_has_fpu(tsk));
if (use_xsave()) {
xsave_state(&tsk->thread.fpu.state->xsave, -1);
if (use_eager_fpu()) {
__save_fpu(tsk);
return;
}
@@ -526,11 +552,9 @@ static inline void fpu_free(struct fpu *fpu)
static inline void fpu_copy(struct task_struct *dst, struct task_struct *src)
{
if (use_xsave()) {
struct xsave_struct *xsave = &dst->thread.fpu.state->xsave;
memset(&xsave->xsave_hdr, 0, sizeof(struct xsave_hdr_struct));
xsave_state(xsave, -1);
if (use_eager_fpu()) {
memset(&dst->thread.fpu.state->xsave, 0, xstate_size);
__save_fpu(dst);
} else {
struct fpu *dfpu = &dst->thread.fpu;
struct fpu *sfpu = &src->thread.fpu;