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powerpc: Add the ability to save FPU without giving it up

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This patch adds the ability to be able to save the FPU registers to the
thread struct without giving up (disabling the facility) next time the
process returns to userspace.

This patch optimises the thread copy path (as a result of a fork() or
clone()) so that the parent thread can return to userspace with hot
registers avoiding a possibly pointless reload of FPU register state.

Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Cyril Bur
2016-02-29 17:53:49 +11:00
committed by Michael Ellerman
parent de2a20aa72
commit 8792468da5
3 changed files with 17 additions and 19 deletions
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3
arch/powerpc/include/asm/switch_to.h
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@@ -28,13 +28,14 @@ extern void giveup_all(struct task_struct *);
extern void enable_kernel_fp(void);
extern void flush_fp_to_thread(struct task_struct *);
extern void giveup_fpu(struct task_struct *);
extern void __giveup_fpu(struct task_struct *);
extern void save_fpu(struct task_struct *);
static inline void disable_kernel_fp(void)
{
msr_check_and_clear(MSR_FP);
}
#else
static inline void __giveup_fpu(struct task_struct *t) { }
static inline void save_fpu(struct task_struct *t) { }
static inline void flush_fp_to_thread(struct task_struct *t) { }
#endif