mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson
synced 2025-09-04 18:49:41 +00:00
730faa15a0
Now that switch_fpu_finish() doesn't load the FPU state, it makes more sense to fold it into switch_fpu_prepare() renamed to switch_fpu(), and more importantly, use the "prev_p" task as a target for TIF_NEED_FPU_LOAD. It doesn't make any sense to delay set_tsk_thread_flag(TIF_NEED_FPU_LOAD) until "prev_p" is scheduled again. There is no worry about the very first context switch, fpu_clone() must always set TIF_NEED_FPU_LOAD. Also, shift the test_tsk_thread_flag(TIF_NEED_FPU_LOAD) from the callers to switch_fpu(). Note that the "PF_KTHREAD | PF_USER_WORKER" check can be removed but this deserves a separate patch which can change more functions, say, kernel_fpu_begin_mask(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Chang S . Bae <chang.seok.bae@intel.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Brian Gerst <brgerst@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Link: https://lore.kernel.org/r/20250503143830.GA8982@redhat.com
56 lines
1.7 KiB
C
56 lines
1.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
#ifndef _ASM_X86_FPU_SCHED_H
|
|
#define _ASM_X86_FPU_SCHED_H
|
|
|
|
#include <linux/sched.h>
|
|
|
|
#include <asm/cpufeature.h>
|
|
#include <asm/fpu/types.h>
|
|
|
|
#include <asm/trace/fpu.h>
|
|
|
|
extern void save_fpregs_to_fpstate(struct fpu *fpu);
|
|
extern void fpu__drop(struct task_struct *tsk);
|
|
extern int fpu_clone(struct task_struct *dst, unsigned long clone_flags, bool minimal,
|
|
unsigned long shstk_addr);
|
|
extern void fpu_flush_thread(void);
|
|
|
|
/*
|
|
* FPU state switching for scheduling.
|
|
*
|
|
* switch_fpu() saves the old state and sets TIF_NEED_FPU_LOAD if
|
|
* TIF_NEED_FPU_LOAD is not set. This is done within the context
|
|
* of the old process.
|
|
*
|
|
* Once TIF_NEED_FPU_LOAD is set, it is required to load the
|
|
* registers before returning to userland or using the content
|
|
* otherwise.
|
|
*
|
|
* The FPU context is only stored/restored for a user task and
|
|
* PF_KTHREAD is used to distinguish between kernel and user threads.
|
|
*/
|
|
static inline void switch_fpu(struct task_struct *old, int cpu)
|
|
{
|
|
if (!test_tsk_thread_flag(old, TIF_NEED_FPU_LOAD) &&
|
|
cpu_feature_enabled(X86_FEATURE_FPU) &&
|
|
!(old->flags & (PF_KTHREAD | PF_USER_WORKER))) {
|
|
struct fpu *old_fpu = x86_task_fpu(old);
|
|
|
|
set_tsk_thread_flag(old, TIF_NEED_FPU_LOAD);
|
|
save_fpregs_to_fpstate(old_fpu);
|
|
/*
|
|
* The save operation preserved register state, so the
|
|
* fpu_fpregs_owner_ctx is still @old_fpu. Store the
|
|
* current CPU number in @old_fpu, so the next return
|
|
* to user space can avoid the FPU register restore
|
|
* when is returns on the same CPU and still owns the
|
|
* context. See fpregs_restore_userregs().
|
|
*/
|
|
old_fpu->last_cpu = cpu;
|
|
|
|
trace_x86_fpu_regs_deactivated(old_fpu);
|
|
}
|
|
}
|
|
|
|
#endif /* _ASM_X86_FPU_SCHED_H */
|