x86/fpu: Get rid of PF_USED_MATH usage, convert it to fpu->fpstate_active
Introduce a simple fpu->fpstate_active flag in the fpu context data structure
and use that instead of PF_USED_MATH in task->flags.
Testing for this flag byte should be slightly more efficient than
testing a bit in a bitmask, but the main advantage is that most
FPU functions can now be performed on a 'struct fpu' alone, they
don't need access to 'struct task_struct' anymore.
There's a slight linecount increase, mostly due to the 'fpu' local
variables and due to extra comments. The local variables will go away
once we move most of the FPU methods to pure 'struct fpu' parameters.
Reviewed-by: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
index bffb2c4..e1ec6f9 100644
--- a/arch/x86/ia32/ia32_signal.c
+++ b/arch/x86/ia32/ia32_signal.c
@@ -307,6 +307,7 @@
size_t frame_size,
void __user **fpstate)
{
+ struct fpu *fpu = ¤t->thread.fpu;
unsigned long sp;
/* Default to using normal stack */
@@ -321,7 +322,7 @@
ksig->ka.sa.sa_restorer)
sp = (unsigned long) ksig->ka.sa.sa_restorer;
- if (current->flags & PF_USED_MATH) {
+ if (fpu->fpstate_active) {
unsigned long fx_aligned, math_size;
sp = alloc_mathframe(sp, 1, &fx_aligned, &math_size);
diff --git a/arch/x86/include/asm/fpu-internal.h b/arch/x86/include/asm/fpu-internal.h
index 2cac49e..9311126 100644
--- a/arch/x86/include/asm/fpu-internal.h
+++ b/arch/x86/include/asm/fpu-internal.h
@@ -375,7 +375,7 @@
__thread_fpu_end(fpu);
}
- tsk->flags &= ~PF_USED_MATH;
+ fpu->fpstate_active = 0;
preempt_enable();
}
@@ -424,7 +424,7 @@
* 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 = (new->flags & PF_USED_MATH) &&
+ fpu.preload = new_fpu->fpstate_active &&
(use_eager_fpu() || new->thread.fpu.counter > 5);
if (old_fpu->has_fpu) {
diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h
index efb520d..f6317d9a 100644
--- a/arch/x86/include/asm/fpu/types.h
+++ b/arch/x86/include/asm/fpu/types.h
@@ -137,6 +137,12 @@
* deal with bursty apps that only use the FPU for a short time:
*/
unsigned char counter;
+ /*
+ * This flag indicates whether this context is fpstate_active: if the task is
+ * not running then we can restore from this context, if the task
+ * is running then we should save into this context.
+ */
+ unsigned char fpstate_active;
};
#endif /* _ASM_X86_FPU_H */
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index d50cc7f..0f4add4 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -385,6 +385,10 @@
unsigned long fs;
#endif
unsigned long gs;
+
+ /* Floating point and extended processor state */
+ struct fpu fpu;
+
/* Save middle states of ptrace breakpoints */
struct perf_event *ptrace_bps[HBP_NUM];
/* Debug status used for traps, single steps, etc... */
@@ -395,8 +399,6 @@
unsigned long cr2;
unsigned long trap_nr;
unsigned long error_code;
- /* floating point and extended processor state */
- struct fpu fpu;
#ifdef CONFIG_X86_32
/* Virtual 86 mode info */
struct vm86_struct __user *vm86_info;
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 7798131..9e7f9e7 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -236,14 +236,17 @@
int fpu__copy(struct task_struct *dst, struct task_struct *src)
{
+ struct fpu *dst_fpu = &dst->thread.fpu;
+ struct fpu *src_fpu = &src->thread.fpu;
+
dst->thread.fpu.counter = 0;
dst->thread.fpu.has_fpu = 0;
dst->thread.fpu.state = NULL;
task_disable_lazy_fpu_restore(dst);
- if (src->flags & PF_USED_MATH) {
- int err = fpstate_alloc(&dst->thread.fpu);
+ if (src_fpu->fpstate_active) {
+ int err = fpstate_alloc(dst_fpu);
if (err)
return err;
@@ -260,11 +263,12 @@
*/
int fpstate_alloc_init(struct task_struct *curr)
{
+ struct fpu *fpu = &curr->thread.fpu;
int ret;
if (WARN_ON_ONCE(curr != current))
return -EINVAL;
- if (WARN_ON_ONCE(curr->flags & PF_USED_MATH))
+ if (WARN_ON_ONCE(fpu->fpstate_active))
return -EINVAL;
/*
@@ -277,7 +281,7 @@
fpstate_init(&curr->thread.fpu);
/* Safe to do for the current task: */
- curr->flags |= PF_USED_MATH;
+ fpu->fpstate_active = 1;
return 0;
}
@@ -308,12 +312,13 @@
*/
static int fpu__unlazy_stopped(struct task_struct *child)
{
+ struct fpu *child_fpu = &child->thread.fpu;
int ret;
if (WARN_ON_ONCE(child == current))
return -EINVAL;
- if (child->flags & PF_USED_MATH) {
+ if (child_fpu->fpstate_active) {
task_disable_lazy_fpu_restore(child);
return 0;
}
@@ -328,7 +333,7 @@
fpstate_init(&child->thread.fpu);
/* Safe to do for stopped child tasks: */
- child->flags |= PF_USED_MATH;
+ child_fpu->fpstate_active = 1;
return 0;
}
@@ -348,7 +353,7 @@
struct task_struct *tsk = current;
struct fpu *fpu = &tsk->thread.fpu;
- if (!(tsk->flags & PF_USED_MATH)) {
+ if (!fpu->fpstate_active) {
local_irq_enable();
/*
* does a slab alloc which can sleep
@@ -378,6 +383,8 @@
void fpu__flush_thread(struct task_struct *tsk)
{
+ struct fpu *fpu = &tsk->thread.fpu;
+
WARN_ON(tsk != current);
if (!use_eager_fpu()) {
@@ -385,7 +392,7 @@
drop_fpu(tsk);
fpstate_free(&tsk->thread.fpu);
} else {
- if (!(tsk->flags & PF_USED_MATH)) {
+ if (!fpu->fpstate_active) {
/* kthread execs. TODO: cleanup this horror. */
if (WARN_ON(fpstate_alloc_init(tsk)))
force_sig(SIGKILL, tsk);
@@ -402,12 +409,16 @@
*/
int fpregs_active(struct task_struct *target, const struct user_regset *regset)
{
- return (target->flags & PF_USED_MATH) ? regset->n : 0;
+ struct fpu *target_fpu = &target->thread.fpu;
+
+ return target_fpu->fpstate_active ? regset->n : 0;
}
int xfpregs_active(struct task_struct *target, const struct user_regset *regset)
{
- return (cpu_has_fxsr && (target->flags & PF_USED_MATH)) ? regset->n : 0;
+ struct fpu *target_fpu = &target->thread.fpu;
+
+ return (cpu_has_fxsr && target_fpu->fpstate_active) ? regset->n : 0;
}
int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
@@ -733,16 +744,17 @@
* struct user_i387_struct) but is in fact only used for 32-bit
* dumps, so on 64-bit it is really struct user_i387_ia32_struct.
*/
-int dump_fpu(struct pt_regs *regs, struct user_i387_struct *fpu)
+int dump_fpu(struct pt_regs *regs, struct user_i387_struct *ufpu)
{
struct task_struct *tsk = current;
+ struct fpu *fpu = &tsk->thread.fpu;
int fpvalid;
- fpvalid = !!(tsk->flags & PF_USED_MATH);
+ fpvalid = fpu->fpstate_active;
if (fpvalid)
fpvalid = !fpregs_get(tsk, NULL,
0, sizeof(struct user_i387_ia32_struct),
- fpu, NULL);
+ ufpu, NULL);
return fpvalid;
}
diff --git a/arch/x86/kernel/fpu/xsave.c b/arch/x86/kernel/fpu/xsave.c
index 8cd1270..dc346e1 100644
--- a/arch/x86/kernel/fpu/xsave.c
+++ b/arch/x86/kernel/fpu/xsave.c
@@ -334,6 +334,7 @@
{
int ia32_fxstate = (buf != buf_fx);
struct task_struct *tsk = current;
+ struct fpu *fpu = &tsk->thread.fpu;
int state_size = xstate_size;
u64 xstate_bv = 0;
int fx_only = 0;
@@ -349,7 +350,7 @@
if (!access_ok(VERIFY_READ, buf, size))
return -EACCES;
- if (!(tsk->flags & PF_USED_MATH) && fpstate_alloc_init(tsk))
+ if (!fpu->fpstate_active && fpstate_alloc_init(tsk))
return -1;
if (!static_cpu_has(X86_FEATURE_FPU))
@@ -384,12 +385,12 @@
int err = 0;
/*
- * Drop the current fpu which clears PF_USED_MATH. This ensures
+ * Drop the current fpu which clears fpu->fpstate_active. This ensures
* that any context-switch during the copy of the new state,
* avoids the intermediate state from getting restored/saved.
* Thus avoiding the new restored state from getting corrupted.
* We will be ready to restore/save the state only after
- * PF_USED_MATH is again set.
+ * fpu->fpstate_active is again set.
*/
drop_fpu(tsk);
@@ -401,7 +402,7 @@
sanitize_restored_xstate(tsk, &env, xstate_bv, fx_only);
}
- tsk->flags |= PF_USED_MATH;
+ fpu->fpstate_active = 1;
if (use_eager_fpu()) {
preempt_disable();
fpu__restore();
@@ -685,7 +686,7 @@
*/
void __init_refok eager_fpu_init(void)
{
- WARN_ON(current->flags & PF_USED_MATH);
+ WARN_ON(current->thread.fpu.fpstate_active);
current_thread_info()->status = 0;
if (eagerfpu == ENABLE)
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 8e2529e..20a9d35 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -198,6 +198,7 @@
unsigned long sp = regs->sp;
unsigned long buf_fx = 0;
int onsigstack = on_sig_stack(sp);
+ struct fpu *fpu = ¤t->thread.fpu;
/* redzone */
if (config_enabled(CONFIG_X86_64))
@@ -217,7 +218,7 @@
}
}
- if (current->flags & PF_USED_MATH) {
+ if (fpu->fpstate_active) {
sp = alloc_mathframe(sp, config_enabled(CONFIG_X86_32),
&buf_fx, &math_size);
*fpstate = (void __user *)sp;
@@ -233,7 +234,7 @@
return (void __user *)-1L;
/* save i387 and extended state */
- if ((current->flags & PF_USED_MATH) &&
+ if (fpu->fpstate_active &&
save_xstate_sig(*fpstate, (void __user *)buf_fx, math_size) < 0)
return (void __user *)-1L;
@@ -616,6 +617,7 @@
handle_signal(struct ksignal *ksig, struct pt_regs *regs)
{
bool stepping, failed;
+ struct fpu *fpu = ¤t->thread.fpu;
/* Are we from a system call? */
if (syscall_get_nr(current, regs) >= 0) {
@@ -664,7 +666,7 @@
/*
* Ensure the signal handler starts with the new fpu state.
*/
- if (current->flags & PF_USED_MATH)
+ if (fpu->fpstate_active)
fpu_reset_state(current);
}
signal_setup_done(failed, ksig, stepping);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0635a1f..bab8afb 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6597,10 +6597,11 @@
int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
{
+ struct fpu *fpu = ¤t->thread.fpu;
int r;
sigset_t sigsaved;
- if (!(current->flags & PF_USED_MATH) && fpstate_alloc_init(current))
+ if (!fpu->fpstate_active && fpstate_alloc_init(current))
return -ENOMEM;
if (vcpu->sigset_active)
diff --git a/arch/x86/math-emu/fpu_entry.c b/arch/x86/math-emu/fpu_entry.c
index bf62880..f1aac55 100644
--- a/arch/x86/math-emu/fpu_entry.c
+++ b/arch/x86/math-emu/fpu_entry.c
@@ -147,8 +147,9 @@
unsigned long code_base = 0;
unsigned long code_limit = 0; /* Initialized to stop compiler warnings */
struct desc_struct code_descriptor;
+ struct fpu *fpu = ¤t->thread.fpu;
- if (!(current->flags & PF_USED_MATH)) {
+ if (!fpu->fpstate_active) {
if (fpstate_alloc_init(current)) {
do_group_exit(SIGKILL);
return;