[PATCH v1 04/31] x86/resctrl: Add helper for setting CPU default properties

James Morse
2024-03-21T16:51:42Z

rdtgroup_rmdir_ctrl() and rdtgroup_rmdir_mon() set the per-CPU
pqr_state for CPUs that were part of the rmdir()'d group.

Another architecture might not have a 'pqr_state', its hardware may
need the values in a different format. MPAM's equivalent of RMID values
are not unique, and always need the CLOSID to be provided too.

There is only one caller that modifies a single value,
(rdtgroup_rmdir_mon()). MPAM always needs both CLOSID and RMID
for the hardware value as these are written to the same system
register.

As rdtgroup_rmdir_mon() has the CLOSID on hand, only provide a
helper to set both values. These values are read by
__resctrl_sched_in(), but may be written by a different CPU without
any locking, add READ/WRTE_ONCE() to avoid torn values.

Signed-off-by: James Morse <james.morse@arm.com>
---
arch/x86/include/asm/resctrl.h | 14 +++++++++++---
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 15 ++++++++++-----
2 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/arch/x86/include/asm/resctrl.h b/arch/x86/include/asm/resctrl.h
index 12dbd2588ca7..f61382258743 100644
--- a/arch/x86/include/asm/resctrl.h
+++ b/arch/x86/include/asm/resctrl.h
@@ -4,8 +4,9 @@

#ifdef CONFIG_X86_CPU_RESCTRL

-#include <linux/sched.h>
#include <linux/jump_label.h>
+#include <linux/percpu.h>
+#include <linux/sched.h>

/*
* This value can never be a valid CLOSID, and is used when mapping a
@@ -96,8 +97,8 @@ static inline void resctrl_arch_disable_mon(void)
static inline void __resctrl_sched_in(struct task_struct *tsk)
{
struct resctrl_pqr_state *state = this_cpu_ptr(&pqr_state);
- u32 closid = state->default_closid;
- u32 rmid = state->default_rmid;
+ u32 closid = READ_ONCE(state->default_closid);
+ u32 rmid = READ_ONCE(state->default_rmid);
u32 tmp;

/*
@@ -132,6 +133,13 @@ static inline unsigned int resctrl_arch_round_mon_val(unsigned int val)
return val * scale;
}

+static inline void resctrl_arch_set_cpu_default_closid_rmid(int cpu, u32 closid,
+ u32 rmid)
+{
+ WRITE_ONCE(per_cpu(pqr_state.default_closid, cpu), closid);
+ WRITE_ONCE(per_cpu(pqr_state.default_rmid, cpu), rmid);
+}
+
static inline void resctrl_arch_set_closid_rmid(struct task_struct *tsk,
u32 closid, u32 rmid)
{
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 45372b6a6215..5d2c1ce5b6b1 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -3623,14 +3623,18 @@ static int rdtgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
static int rdtgroup_rmdir_mon(struct rdtgroup *rdtgrp, cpumask_var_t tmpmask)
{
struct rdtgroup *prdtgrp = rdtgrp->mon.parent;
+ u32 closid, rmid;
int cpu;

/* Give any tasks back to the parent group */
rdt_move_group_tasks(rdtgrp, prdtgrp, tmpmask);

/* Update per cpu rmid of the moved CPUs first */
+ closid = rdtgrp->closid;
+ rmid = prdtgrp->mon.rmid;
for_each_cpu(cpu, &rdtgrp->cpu_mask)
- per_cpu(pqr_state.default_rmid, cpu) = prdtgrp->mon.rmid;
+ resctrl_arch_set_cpu_default_closid_rmid(cpu, closid, rmid);
+
/*
* Update the MSR on moved CPUs and CPUs which have moved
* task running on them.
@@ -3663,6 +3667,7 @@ static int rdtgroup_ctrl_remove(struct rdtgroup *rdtgrp)

static int rdtgroup_rmdir_ctrl(struct rdtgroup *rdtgrp, cpumask_var_t tmpmask)
{
+ u32 closid, rmid;
int cpu;

/* Give any tasks back to the default group */
@@ -3673,10 +3678,10 @@ static int rdtgroup_rmdir_ctrl(struct rdtgroup *rdtgrp, cpumask_var_t tmpmask)
&rdtgroup_default.cpu_mask, &rdtgrp->cpu_mask);

/* Update per cpu closid and rmid of the moved CPUs first */
- for_each_cpu(cpu, &rdtgrp->cpu_mask) {
- per_cpu(pqr_state.default_closid, cpu) = rdtgroup_default.closid;
- per_cpu(pqr_state.default_rmid, cpu) = rdtgroup_default.mon.rmid;
- }
+ closid = rdtgroup_default.closid;
+ rmid = rdtgroup_default.mon.rmid;
+ for_each_cpu(cpu, &rdtgrp->cpu_mask)
+ resctrl_arch_set_cpu_default_closid_rmid(cpu, closid, rmid);

/*
* Update the MSR on moved CPUs and CPUs which have moved
--
2.39.2