Commit b0fb2938 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'x86_cache_for_v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull x86 resource control updates from Borislav Petkov:
 "Avoid IPI-ing a task in certain cases and prevent load/store tearing
  when accessing a task's resctrl fields concurrently"

* tag 'x86_cache_for_v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/resctrl: Apply READ_ONCE/WRITE_ONCE to task_struct.{rmid,closid}
  x86/resctrl: Use task_curr() instead of task_struct->on_cpu to prevent unnecessary IPI
  x86/resctrl: Add printf attribute to log function
parents 0570b693 6d3b47dd

arch/x86/include/asm/resctrl.h

+7 −4
Original line number Diff line number Diff line
@@ -56,19 +56,22 @@ static void __resctrl_sched_in(void) 
	struct resctrl_pqr_state *state = this_cpu_ptr(&pqr_state);

	u32 closid = state->default_closid;

	u32 rmid = state->default_rmid;

	u32 tmp;



	/*

	 * If this task has a closid/rmid assigned, use it.

	 * Else use the closid/rmid assigned to this cpu.

	 */

	if (static_branch_likely(&rdt_alloc_enable_key)) {

		if (current->closid)

			closid = current->closid;

		tmp = READ_ONCE(current->closid);

		if (tmp)

			closid = tmp;

	}



	if (static_branch_likely(&rdt_mon_enable_key)) {

		if (current->rmid)

			rmid = current->rmid;

		tmp = READ_ONCE(current->rmid);

		if (tmp)

			rmid = tmp;

	}



	if (closid != state->cur_closid || rmid != state->cur_rmid) {

arch/x86/kernel/cpu/resctrl/internal.h

+1 −0
Original line number Diff line number Diff line
@@ -572,6 +572,7 @@ union cpuid_0x10_x_edx { 


void rdt_last_cmd_clear(void);

void rdt_last_cmd_puts(const char *s);

__printf(1, 2)

void rdt_last_cmd_printf(const char *fmt, ...);



void rdt_ctrl_update(void *arg);

arch/x86/kernel/cpu/resctrl/rdtgroup.c

+10 −14
Original line number Diff line number Diff line
@@ -563,11 +563,11 @@ static int __rdtgroup_move_task(struct task_struct *tsk, 
	 */



	if (rdtgrp->type == RDTCTRL_GROUP) {

		tsk->closid = rdtgrp->closid;

		tsk->rmid = rdtgrp->mon.rmid;

		WRITE_ONCE(tsk->closid, rdtgrp->closid);

		WRITE_ONCE(tsk->rmid, rdtgrp->mon.rmid);

	} else if (rdtgrp->type == RDTMON_GROUP) {

		if (rdtgrp->mon.parent->closid == tsk->closid) {

			tsk->rmid = rdtgrp->mon.rmid;

			WRITE_ONCE(tsk->rmid, rdtgrp->mon.rmid);

		} else {

			rdt_last_cmd_puts("Can't move task to different control group\n");

			return -EINVAL;
@@ -2310,22 +2310,18 @@ static void rdt_move_group_tasks(struct rdtgroup *from, struct rdtgroup *to, 
	for_each_process_thread(p, t) {

		if (!from || is_closid_match(t, from) ||

		    is_rmid_match(t, from)) {

			t->closid = to->closid;

			t->rmid = to->mon.rmid;

			WRITE_ONCE(t->closid, to->closid);

			WRITE_ONCE(t->rmid, to->mon.rmid);



#ifdef CONFIG_SMP

			/*

			 * This is safe on x86 w/o barriers as the ordering

			 * of writing to task_cpu() and t->on_cpu is

			 * reverse to the reading here. The detection is

			 * inaccurate as tasks might move or schedule

			 * before the smp function call takes place. In

			 * such a case the function call is pointless, but

			 * If the task is on a CPU, set the CPU in the mask.

			 * The detection is inaccurate as tasks might move or

			 * schedule before the smp function call takes place.

			 * In such a case the function call is pointless, but

			 * there is no other side effect.

			 */

			if (mask && t->on_cpu)

			if (IS_ENABLED(CONFIG_SMP) && mask && task_curr(t))

				cpumask_set_cpu(task_cpu(t), mask);

#endif

		}

	}

	read_unlock(&tasklist_lock);