cb3ea4b767
We don't set it on PF_KTHREAD threads as they never return to userspace, and PF_IO_WORKER threads are identical in that regard. As they keep running in the kernel until they die, skip setting the FPU flag on them. More of a cosmetic thing that was found while debugging and issue and pondering why the FPU flag is set on these threads. Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Ingo Molnar <mingo@kernel.org> Acked-by: Peter Zijlstra <peterz@infradead.org> Link: https://lore.kernel.org/r/560c844c-f128-555b-40c6-31baff27537f@kernel.dk
84 lines
2.4 KiB
C
84 lines
2.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __X86_KERNEL_FPU_CONTEXT_H
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#define __X86_KERNEL_FPU_CONTEXT_H
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#include <asm/fpu/xstate.h>
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#include <asm/trace/fpu.h>
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/* Functions related to FPU context tracking */
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/*
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* The in-register FPU state for an FPU context on a CPU is assumed to be
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* valid if the fpu->last_cpu matches the CPU, and the fpu_fpregs_owner_ctx
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* matches the FPU.
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*
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* If the FPU register state is valid, the kernel can skip restoring the
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* FPU state from memory.
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*
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* Any code that clobbers the FPU registers or updates the in-memory
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* FPU state for a task MUST let the rest of the kernel know that the
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* FPU registers are no longer valid for this task.
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*
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* Either one of these invalidation functions is enough. Invalidate
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* a resource you control: CPU if using the CPU for something else
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* (with preemption disabled), FPU for the current task, or a task that
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* is prevented from running by the current task.
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*/
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static inline void __cpu_invalidate_fpregs_state(void)
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{
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__this_cpu_write(fpu_fpregs_owner_ctx, NULL);
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}
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static inline void __fpu_invalidate_fpregs_state(struct fpu *fpu)
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{
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fpu->last_cpu = -1;
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}
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static inline int fpregs_state_valid(struct fpu *fpu, unsigned int cpu)
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{
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return fpu == this_cpu_read(fpu_fpregs_owner_ctx) && cpu == fpu->last_cpu;
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}
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static inline void fpregs_deactivate(struct fpu *fpu)
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{
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__this_cpu_write(fpu_fpregs_owner_ctx, NULL);
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trace_x86_fpu_regs_deactivated(fpu);
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}
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static inline void fpregs_activate(struct fpu *fpu)
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{
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__this_cpu_write(fpu_fpregs_owner_ctx, fpu);
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trace_x86_fpu_regs_activated(fpu);
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}
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/* Internal helper for switch_fpu_return() and signal frame setup */
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static inline void fpregs_restore_userregs(void)
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{
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struct fpu *fpu = ¤t->thread.fpu;
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int cpu = smp_processor_id();
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if (WARN_ON_ONCE(current->flags & (PF_KTHREAD | PF_IO_WORKER)))
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return;
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if (!fpregs_state_valid(fpu, cpu)) {
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/*
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* This restores _all_ xstate which has not been
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* established yet.
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*
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* If PKRU is enabled, then the PKRU value is already
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* correct because it was either set in switch_to() or in
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* flush_thread(). So it is excluded because it might be
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* not up to date in current->thread.fpu.xsave state.
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*
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* XFD state is handled in restore_fpregs_from_fpstate().
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*/
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restore_fpregs_from_fpstate(fpu->fpstate, XFEATURE_MASK_FPSTATE);
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fpregs_activate(fpu);
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fpu->last_cpu = cpu;
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}
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clear_thread_flag(TIF_NEED_FPU_LOAD);
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}
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#endif
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