[PATCH v4 02/24] x86/resctrl: Access per-rmid structures by index

From: James Morse
Date: Thu May 25 2023 - 14:02:51 EST

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Because of the differences between Intel RDT/AMD QoS and Arm's MPAM
monitors, RMID values on arm64 are not unique unless the CLOSID is
also included. Bitmaps like rmid_busy_llc need to be sized by the
number of unique entries for this resource.

Add helpers to encode/decode the CLOSID and RMID to an index. The
domain's rmid_busy_llc and rmid_ptrs[] are then sized by index,
as are the domain mbm_local and mbm_total arrays.
On x86, the index is always just the RMID, so all these structures
remain the same size.

The index gives resctrl a unique value it can use to store monitor
values, and allows MPAM to decode the CLOSID when reading the hardware
counters.

Tested-by: Shaopeng Tan <tan.shaopeng@xxxxxxxxxxx>
Signed-off-by: James Morse <james.morse@xxxxxxx>
---
Changes since v1:
* Added X86_BAD_CLOSID macro to make it clear what this value means
* Added second WARN_ON() for closid checking, and made both _ONCE()

Changes since v2:
* Added RESCTRL_RESERVED_CLOSID
* Removed a newline
* Repharsed some comments
* Renamed a variable 'ignore'd
* Moved X86_RESCTRL_BAD_CLOSID to a previous patch

Changes since v3:
* Changed a variable name
* Fixed various typos
---
arch/x86/include/asm/resctrl.h | 17 ++++++
arch/x86/kernel/cpu/resctrl/core.c | 2 +-
arch/x86/kernel/cpu/resctrl/internal.h | 1 +
arch/x86/kernel/cpu/resctrl/monitor.c | 84 +++++++++++++++++---------
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 7 ++-
include/linux/resctrl.h | 3 +
6 files changed, 83 insertions(+), 31 deletions(-)

diff --git a/arch/x86/include/asm/resctrl.h b/arch/x86/include/asm/resctrl.h
index e906070285fb..dd9b638d43c8 100644
--- a/arch/x86/include/asm/resctrl.h
+++ b/arch/x86/include/asm/resctrl.h
@@ -101,6 +101,23 @@ static inline void resctrl_sched_in(struct task_struct *tsk)
__resctrl_sched_in(tsk);
}

+static inline u32 resctrl_arch_system_num_rmid_idx(void)
+{
+ /* RMID are independent numbers for x86. num_rmid_idx == num_rmid */
+ return boot_cpu_data.x86_cache_max_rmid + 1;
+}
+
+static inline void resctrl_arch_rmid_idx_decode(u32 idx, u32 *closid, u32 *rmid)
+{
+ *rmid = idx;
+ *closid = X86_RESCTRL_BAD_CLOSID;
+}
+
+static inline u32 resctrl_arch_rmid_idx_encode(u32 ignored, u32 rmid)
+{
+ return rmid;
+}
+
void resctrl_cpu_detect(struct cpuinfo_x86 *c);

#else
diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
index 030d3b409768..4bea032d072e 100644
--- a/arch/x86/kernel/cpu/resctrl/core.c
+++ b/arch/x86/kernel/cpu/resctrl/core.c
@@ -600,7 +600,7 @@ static void clear_closid_rmid(int cpu)
state->default_rmid = 0;
state->cur_closid = 0;
state->cur_rmid = 0;
- wrmsr(MSR_IA32_PQR_ASSOC, 0, 0);
+ wrmsr(MSR_IA32_PQR_ASSOC, 0, RESCTRL_RESERVED_CLOSID);
}

static int resctrl_online_cpu(unsigned int cpu)
diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index f2da908bb079..d571da4848a4 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -7,6 +7,7 @@
#include <linux/kernfs.h>
#include <linux/fs_context.h>
#include <linux/jump_label.h>
+#include <asm/resctrl.h>

#define L3_QOS_CDP_ENABLE 0x01ULL

diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
index 86574adedd64..bcc25f5339c0 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -142,12 +142,29 @@ static inline u64 get_corrected_mbm_count(u32 rmid, unsigned long val)
return val;
}

-static inline struct rmid_entry *__rmid_entry(u32 closid, u32 rmid)
+/*
+ * x86 and arm64 differ in their handling of monitoring.
+ * x86's RMID are an independent number, there is only one source of traffic
+ * with an RMID value of '1'.
+ * arm64's PMG extend the PARTID/CLOSID space, there are multiple sources of
+ * traffic with a PMG value of '1', one for each CLOSID, meaning the RMID
+ * value is no longer unique.
+ * To account for this, resctrl uses an index. On x86 this is just the RMID,
+ * on arm64 it encodes the CLOSID and RMID. This gives a unique number.
+ *
+ * The domain's rmid_busy_llc and rmid_ptrs are sized by index. The arch code
+ * must accept an attempt to read every index.
+ */
+static inline struct rmid_entry *__rmid_entry(u32 idx)
{
struct rmid_entry *entry;
+ u32 closid, rmid;

- entry = &rmid_ptrs[rmid];
- WARN_ON(entry->rmid != rmid);
+ entry = &rmid_ptrs[idx];
+ resctrl_arch_rmid_idx_decode(idx, &closid, &rmid);
+
+ WARN_ON_ONCE(entry->closid != closid);
+ WARN_ON_ONCE(entry->rmid != rmid);

return entry;
}
@@ -277,8 +294,9 @@ int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_domain *d,
void __check_limbo(struct rdt_domain *d, bool force_free)
{
struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
+ u32 idx_limit = resctrl_arch_system_num_rmid_idx();
struct rmid_entry *entry;
- u32 crmid = 1, nrmid;
+ u32 idx, cur_idx = 1;
bool rmid_dirty;
u64 val = 0;

@@ -289,12 +307,11 @@ void __check_limbo(struct rdt_domain *d, bool force_free)
* RMID and move it to the free list when the counter reaches 0.
*/
for (;;) {
- nrmid = find_next_bit(d->rmid_busy_llc, r->num_rmid, crmid);
- if (nrmid >= r->num_rmid)
+ idx = find_next_bit(d->rmid_busy_llc, idx_limit, cur_idx);
+ if (idx >= idx_limit)
break;

- entry = __rmid_entry(X86_RESCTRL_BAD_CLOSID, nrmid);// temporary
-
+ entry = __rmid_entry(idx);
if (resctrl_arch_rmid_read(r, d, entry->closid, entry->rmid,
QOS_L3_OCCUP_EVENT_ID, &val)) {
rmid_dirty = true;
@@ -303,19 +320,21 @@ void __check_limbo(struct rdt_domain *d, bool force_free)
}

if (force_free || !rmid_dirty) {
- clear_bit(entry->rmid, d->rmid_busy_llc);
+ clear_bit(idx, d->rmid_busy_llc);
if (!--entry->busy) {
rmid_limbo_count--;
list_add_tail(&entry->list, &rmid_free_lru);
}
}
- crmid = nrmid + 1;
+ cur_idx = idx + 1;
}
}

bool has_busy_rmid(struct rdt_resource *r, struct rdt_domain *d)
{
- return find_first_bit(d->rmid_busy_llc, r->num_rmid) != r->num_rmid;
+ u32 idx_limit = resctrl_arch_system_num_rmid_idx();
+
+ return find_first_bit(d->rmid_busy_llc, idx_limit) != idx_limit;
}

/*
@@ -345,6 +364,9 @@ static void add_rmid_to_limbo(struct rmid_entry *entry)
struct rdt_domain *d;
int cpu, err;
u64 val = 0;
+ u32 idx;
+
+ idx = resctrl_arch_rmid_idx_encode(entry->closid, entry->rmid);

entry->busy = 0;
cpu = get_cpu();
@@ -364,7 +386,7 @@ static void add_rmid_to_limbo(struct rmid_entry *entry)
*/
if (!has_busy_rmid(r, d))
cqm_setup_limbo_handler(d, CQM_LIMBOCHECK_INTERVAL);
- set_bit(entry->rmid, d->rmid_busy_llc);
+ set_bit(idx, d->rmid_busy_llc);
entry->busy++;
}
put_cpu();
@@ -377,14 +399,16 @@ static void add_rmid_to_limbo(struct rmid_entry *entry)

void free_rmid(u32 closid, u32 rmid)
{
+ u32 idx = resctrl_arch_rmid_idx_encode(closid, rmid);
struct rmid_entry *entry;

- if (!rmid)
- return;
-
lockdep_assert_held(&rdtgroup_mutex);

- entry = __rmid_entry(closid, rmid);
+ /* do not allow the default rmid to be free'd */
+ if (!idx)
+ return;
+
+ entry = __rmid_entry(idx);

if (is_llc_occupancy_enabled())
add_rmid_to_limbo(entry);
@@ -395,11 +419,13 @@ void free_rmid(u32 closid, u32 rmid)
static struct mbm_state *get_mbm_state(struct rdt_domain *d, u32 closid,
u32 rmid, enum resctrl_event_id evtid)
{
+ u32 idx = resctrl_arch_rmid_idx_encode(closid, rmid);
+
switch (evtid) {
case QOS_L3_MBM_TOTAL_EVENT_ID:
- return &d->mbm_total[rmid];
+ return &d->mbm_total[idx];
case QOS_L3_MBM_LOCAL_EVENT_ID:
- return &d->mbm_local[rmid];
+ return &d->mbm_local[idx];
default:
return NULL;
}
@@ -441,7 +467,8 @@ static int __mon_event_count(u32 closid, u32 rmid, struct rmid_read *rr)
*/
static void mbm_bw_count(u32 closid, u32 rmid, struct rmid_read *rr)
{
- struct mbm_state *m = &rr->d->mbm_local[rmid];
+ u32 idx = resctrl_arch_rmid_idx_encode(closid, rmid);
+ struct mbm_state *m = &rr->d->mbm_local[idx];
u64 cur_bw, bytes, cur_bytes;

cur_bytes = rr->val;
@@ -531,7 +558,7 @@ static void update_mba_bw(struct rdtgroup *rgrp, struct rdt_domain *dom_mbm)
{
u32 closid, rmid, cur_msr_val, new_msr_val;
struct mbm_state *pmbm_data, *cmbm_data;
- u32 cur_bw, delta_bw, user_bw;
+ u32 cur_bw, delta_bw, user_bw, idx;
struct rdt_resource *r_mba;
struct rdt_domain *dom_mba;
struct list_head *head;
@@ -544,7 +571,8 @@ static void update_mba_bw(struct rdtgroup *rgrp, struct rdt_domain *dom_mbm)

closid = rgrp->closid;
rmid = rgrp->mon.rmid;
- pmbm_data = &dom_mbm->mbm_local[rmid];
+ idx = resctrl_arch_rmid_idx_encode(closid, rmid);
+ pmbm_data = &dom_mbm->mbm_local[idx];

dom_mba = get_domain_from_cpu(smp_processor_id(), r_mba);
if (!dom_mba) {
@@ -727,19 +755,20 @@ void mbm_setup_overflow_handler(struct rdt_domain *dom, unsigned long delay_ms)

static int dom_data_init(struct rdt_resource *r)
{
+ u32 idx_limit = resctrl_arch_system_num_rmid_idx();
struct rmid_entry *entry = NULL;
- int i, nr_rmids;
+ u32 idx;
+ int i;

- nr_rmids = r->num_rmid;
- rmid_ptrs = kcalloc(nr_rmids, sizeof(struct rmid_entry), GFP_KERNEL);
+ rmid_ptrs = kcalloc(idx_limit, sizeof(struct rmid_entry), GFP_KERNEL);
if (!rmid_ptrs)
return -ENOMEM;

- for (i = 0; i < nr_rmids; i++) {
+ for (i = 0; i < idx_limit; i++) {
entry = &rmid_ptrs[i];
INIT_LIST_HEAD(&entry->list);

- entry->rmid = i;
+ resctrl_arch_rmid_idx_decode(i, &entry->closid, &entry->rmid);
list_add_tail(&entry->list, &rmid_free_lru);
}

@@ -748,7 +777,8 @@ static int dom_data_init(struct rdt_resource *r)
* default_rdtgroup control group, which will be setup later. See
* rdtgroup_setup_root().
*/
- entry = __rmid_entry(0, 0);
+ idx = resctrl_arch_rmid_idx_encode(RESCTRL_RESERVED_CLOSID, 0);
+ entry = __rmid_entry(idx);
list_del(&entry->list);

return 0;
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index ff9ccfcd18bd..023eae69f29e 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -3604,16 +3604,17 @@ void resctrl_offline_domain(struct rdt_resource *r, struct rdt_domain *d)

static int domain_setup_mon_state(struct rdt_resource *r, struct rdt_domain *d)
{
+ u32 idx_limit = resctrl_arch_system_num_rmid_idx();
size_t tsize;

if (is_llc_occupancy_enabled()) {
- d->rmid_busy_llc = bitmap_zalloc(r->num_rmid, GFP_KERNEL);
+ d->rmid_busy_llc = bitmap_zalloc(idx_limit, GFP_KERNEL);
if (!d->rmid_busy_llc)
return -ENOMEM;
}
if (is_mbm_total_enabled()) {
tsize = sizeof(*d->mbm_total);
- d->mbm_total = kcalloc(r->num_rmid, tsize, GFP_KERNEL);
+ d->mbm_total = kcalloc(idx_limit, tsize, GFP_KERNEL);
if (!d->mbm_total) {
bitmap_free(d->rmid_busy_llc);
return -ENOMEM;
@@ -3621,7 +3622,7 @@ static int domain_setup_mon_state(struct rdt_resource *r, struct rdt_domain *d)
}
if (is_mbm_local_enabled()) {
tsize = sizeof(*d->mbm_local);
- d->mbm_local = kcalloc(r->num_rmid, tsize, GFP_KERNEL);
+ d->mbm_local = kcalloc(idx_limit, tsize, GFP_KERNEL);
if (!d->mbm_local) {
bitmap_free(d->rmid_busy_llc);
kfree(d->mbm_total);
diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
index 7d80bae05f59..ff7452f644e4 100644
--- a/include/linux/resctrl.h
+++ b/include/linux/resctrl.h
@@ -6,6 +6,9 @@
#include <linux/list.h>
#include <linux/pid.h>

+/* CLOSID value used by the default control group */
+#define RESCTRL_RESERVED_CLOSID 0
+
#ifdef CONFIG_PROC_CPU_RESCTRL

int proc_resctrl_show(struct seq_file *m,
--
2.39.2

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