powerpc: Add support for setting SPRN_TIDR (ec233ede) · Commits · 戴 / test

arch/powerpc/include/asm/processor.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -329,6 +329,7 @@ struct thread_struct {
		*/
		int dscr_inherit;
		unsigned long ppr; /* used to save/restore SMT priority */
		unsigned long tidr;
		#endif
		#ifdef CONFIG_PPC_BOOK3S_64
		unsigned long tar;

arch/powerpc/include/asm/switch_to.h

+3 −0

Original line number	Diff line number	Diff line
		@@ -91,4 +91,7 @@ static inline void clear_task_ebb(struct task_struct *t)
		#endif
		}

		extern int set_thread_tidr(struct task_struct *t);
		extern void clear_thread_tidr(struct task_struct *t);

		#endif /* _ASM_POWERPC_SWITCH_TO_H */

arch/powerpc/kernel/process.c

+116 −0

Original line number	Diff line number	Diff line
		@@ -1136,6 +1136,10 @@ static inline void restore_sprs(struct thread_struct *old_thread,
		if (old_thread->tar != new_thread->tar)
		mtspr(SPRN_TAR, new_thread->tar);
		}

		if (cpu_has_feature(CPU_FTR_ARCH_300) &&
		old_thread->tidr != new_thread->tidr)
		mtspr(SPRN_TIDR, new_thread->tidr);
		#endif
		}

		@@ -1451,6 +1455,116 @@ void flush_thread(void)
		#endif /* CONFIG_HAVE_HW_BREAKPOINT */
		}

		#ifdef CONFIG_PPC64
		static DEFINE_SPINLOCK(vas_thread_id_lock);
		static DEFINE_IDA(vas_thread_ida);

		/*
		* We need to assign a unique thread id to each thread in a process.
		*
		* This thread id, referred to as TIDR, and separate from the Linux's tgid,
		* is intended to be used to direct an ASB_Notify from the hardware to the
		* thread, when a suitable event occurs in the system.
		*
		* One such event is a "paste" instruction in the context of Fast Thread
		* Wakeup (aka Core-to-core wake up in the Virtual Accelerator Switchboard
		* (VAS) in POWER9.
		*
		* To get a unique TIDR per process we could simply reuse task_pid_nr() but
		* the problem is that task_pid_nr() is not yet available copy_thread() is
		* called. Fixing that would require changing more intrusive arch-neutral
		* code in code path in copy_process()?.
		*
		* Further, to assign unique TIDRs within each process, we need an atomic
		* field (or an IDR) in task_struct, which again intrudes into the arch-
		* neutral code. So try to assign globally unique TIDRs for now.
		*
		* NOTE: TIDR 0 indicates that the thread does not need a TIDR value.
		* For now, only threads that expect to be notified by the VAS
		* hardware need a TIDR value and we assign values > 0 for those.
		*/
		#define MAX_THREAD_CONTEXT ((1 << 16) - 1)
		static int assign_thread_tidr(void)
		{
		int index;
		int err;

		again:
		if (!ida_pre_get(&vas_thread_ida, GFP_KERNEL))
		return -ENOMEM;

		spin_lock(&vas_thread_id_lock);
		err = ida_get_new_above(&vas_thread_ida, 1, &index);
		spin_unlock(&vas_thread_id_lock);

		if (err == -EAGAIN)
		goto again;
		else if (err)
		return err;

		if (index > MAX_THREAD_CONTEXT) {
		spin_lock(&vas_thread_id_lock);
		ida_remove(&vas_thread_ida, index);
		spin_unlock(&vas_thread_id_lock);
		return -ENOMEM;
		}

		return index;
		}

		static void free_thread_tidr(int id)
		{
		spin_lock(&vas_thread_id_lock);
		ida_remove(&vas_thread_ida, id);
		spin_unlock(&vas_thread_id_lock);
		}

		/*
		* Clear any TIDR value assigned to this thread.
		*/
		void clear_thread_tidr(struct task_struct *t)
		{
		if (!t->thread.tidr)
		return;

		if (!cpu_has_feature(CPU_FTR_ARCH_300)) {
		WARN_ON_ONCE(1);
		return;
		}

		mtspr(SPRN_TIDR, 0);
		free_thread_tidr(t->thread.tidr);
		t->thread.tidr = 0;
		}

		void arch_release_task_struct(struct task_struct *t)
		{
		clear_thread_tidr(t);
		}

		/*
		* Assign a unique TIDR (thread id) for task @t and set it in the thread
		* structure. For now, we only support setting TIDR for 'current' task.
		*/
		int set_thread_tidr(struct task_struct *t)
		{
		if (!cpu_has_feature(CPU_FTR_ARCH_300))
		return -EINVAL;

		if (t != current)
		return -EINVAL;

		t->thread.tidr = assign_thread_tidr();
		if (t->thread.tidr < 0)
		return t->thread.tidr;

		mtspr(SPRN_TIDR, t->thread.tidr);

		return 0;
		}

		#endif /* CONFIG_PPC64 */

		void
		release_thread(struct task_struct *t)
		{
		@@ -1597,6 +1711,8 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
		}
		if (cpu_has_feature(CPU_FTR_HAS_PPR))
		p->thread.ppr = INIT_PPR;

		p->thread.tidr = 0;
		#endif
		kregs->nip = ppc_function_entry(f);
		return 0;

Admin message