diff options
| -rw-r--r-- | arch/x86/kernel/fpu/core.c | 51 |
1 files changed, 19 insertions, 32 deletions
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index 6b0955a..86a9a9a 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -322,47 +322,34 @@ void fpu__activate_fpstate_read(struct fpu *fpu) } /* - * This function must be called before we read or write a task's fpstate. + * This function must be called before we write a task's fpstate. * - * If the task has not used the FPU before then initialize its - * fpstate. - * - * If the task has used the FPU before then save and unlazy it. - * - * [ If this function is used for non-current child tasks, then - * after this function call, after registers in the fpstate are - * modified and the child task has woken up, the child task will - * restore the modified FPU state from the modified context. If we - * didn't clear its lazy status here then the lazy in-registers - * state pending on its former CPU could be restored, corrupting - * the modifications. + * If the task has used the FPU before then unlazy it. + * If the task has not used the FPU before then initialize its fpstate. * - * This function can be used for the current task as well, but - * only for reading the fpstate. Modifications to the fpstate - * will be lost on eagerfpu systems. ] - * - * TODO: A future optimization would be to skip the unlazying in - * the read-only case, it's not strictly necessary for - * read-only access to the context. + * After this function call, after registers in the fpstate are + * modified and the child task has woken up, the child task will + * restore the modified FPU state from the modified context. If we + * didn't clear its lazy status here then the lazy in-registers + * state pending on its former CPU could be restored, corrupting + * the modifications. */ void fpu__activate_fpstate_write(struct fpu *fpu) { /* - * If fpregs are active (in the current CPU), then - * copy them to the fpstate: + * Only stopped child tasks can be used to modify the FPU + * state in the fpstate buffer: */ - if (fpu->fpregs_active) { - fpu__save(fpu); + WARN_ON_FPU(fpu == ¤t->thread.fpu); + + if (fpu->fpstate_active) { + /* Invalidate any lazy state: */ + fpu->last_cpu = -1; } else { - if (fpu->fpstate_active) { - /* Invalidate any lazy state: */ - fpu->last_cpu = -1; - } else { - fpstate_init(&fpu->state); + fpstate_init(&fpu->state); - /* Safe to do for current and for stopped child tasks: */ - fpu->fpstate_active = 1; - } + /* Safe to do for stopped child tasks: */ + fpu->fpstate_active = 1; } } |