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Avoid IPI-ing a task in certain cases and prevent load/store tearing 

when accessing a task's resctrl fields concurrently.
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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
This commit is contained in:
Linus Torvalds 2021-02-20 20:39:04 -08:00
parent 0570b69305 6d3b47ddff
commit b0fb29382d
3 changed files with 18 additions and 18 deletions
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11
arch/x86/include/asm/resctrl.h
View File

@ -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) {

1
arch/x86/kernel/cpu/resctrl/internal.h
View File

@ -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);

24
arch/x86/kernel/cpu/resctrl/rdtgroup.c
View File

@ -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);