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x86/resctrl: Apply READ_ONCE/WRITE_ONCE to task_struct.{rmid,closid} 

A CPU's current task can have its {closid, rmid} fields read locally
while they are being concurrently written to from another CPU.
This can happen anytime __resctrl_sched_in() races with either
__rdtgroup_move_task() or rdt_move_group_tasks().

Prevent load / store tearing for those accesses by giving them the
READ_ONCE() / WRITE_ONCE() treatment.

Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/9921fda88ad81afb9885b517fbe864a2bc7c35a9.1608243147.git.reinette.chatre@intel.com
This commit is contained in:
Valentin Schneider 2020-12-17 14:31:21 -08:00 committed by Borislav Petkov
parent e0ad6dc896
commit 6d3b47ddff
2 changed files with 12 additions and 9 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) {

10
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;
@ -2310,8 +2310,8 @@ 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);
/*
* If the task is on a CPU, set the CPU in the mask.