[tip: x86/cache] x86/resctrl: Abstract __rmid_read()

From: tip-bot2 for James Morse
Date: Fri Sep 23 2022 - 14:02:21 EST

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The following commit has been merged into the x86/cache branch of tip:

Commit-ID: 4d044c521a63b2cd394ea6e3547012032145e47e
Gitweb: https://git.kernel.org/tip/4d044c521a63b2cd394ea6e3547012032145e47e
Author: James Morse <james.morse@xxxxxxx>
AuthorDate: Fri, 02 Sep 2022 15:48:23
Committer: Borislav Petkov <bp@xxxxxxx>
CommitterDate: Fri, 23 Sep 2022 14:17:20 +02:00

x86/resctrl: Abstract __rmid_read()

__rmid_read() selects the specified eventid and returns the counter
value from the MSR. The error handling is architecture specific, and
handled by the callers, rdtgroup_mondata_show() and __mon_event_count().

Error handling should be handled by architecture specific code, as
a different architecture may have different requirements. MPAM's
counters can report that they are 'not ready', requiring a second
read after a short delay. This should be hidden from resctrl.

Make __rmid_read() the architecture specific function for reading
a counter. Rename it resctrl_arch_rmid_read() and move the error
handling into it.

A read from a counter that hardware supports but resctrl does not
now returns -EINVAL instead of -EIO from the default case in
__mon_event_count(). It isn't possible for user-space to see this
change as resctrl doesn't expose counters it doesn't support.

Signed-off-by: James Morse <james.morse@xxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Reviewed-by: Jamie Iles <quic_jiles@xxxxxxxxxxx>
Reviewed-by: Shaopeng Tan <tan.shaopeng@xxxxxxxxxxx>
Reviewed-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
Tested-by: Xin Hao <xhao@xxxxxxxxxxxxxxxxx>
Tested-by: Shaopeng Tan <tan.shaopeng@xxxxxxxxxxx>
Tested-by: Cristian Marussi <cristian.marussi@xxxxxxx>
Link: https://lore.kernel.org/r/20220902154829.30399-16-james.morse@xxxxxxx
---
arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 4 +-
arch/x86/kernel/cpu/resctrl/internal.h | 1 +-
arch/x86/kernel/cpu/resctrl/monitor.c | 62 +++++++++++++---------
include/linux/resctrl.h | 1 +-
4 files changed, 43 insertions(+), 25 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
index 0ab9232..42a1abb 100644
--- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
+++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
@@ -579,9 +579,9 @@ int rdtgroup_mondata_show(struct seq_file *m, void *arg)

mon_event_read(&rr, r, d, rdtgrp, evtid, false);

- if (rr.val & RMID_VAL_ERROR)
+ if (rr.err == -EIO)
seq_puts(m, "Error\n");
- else if (rr.val & RMID_VAL_UNAVAIL)
+ else if (rr.err == -EINVAL)
seq_puts(m, "Unavailable\n");
else
seq_printf(m, "%llu\n", rr.val * hw_res->mon_scale);
diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index b34a140..1d2e7bd 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -94,6 +94,7 @@ struct rmid_read {
struct rdt_domain *d;
enum resctrl_event_id evtid;
bool first;
+ int err;
u64 val;
};

diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
index e975514..51ab76f 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -167,9 +167,9 @@ void resctrl_arch_reset_rmid(struct rdt_resource *r, struct rdt_domain *d,
memset(am, 0, sizeof(*am));
}

-static u64 __rmid_read(u32 rmid, enum resctrl_event_id eventid)
+int resctrl_arch_rmid_read(u32 rmid, enum resctrl_event_id eventid, u64 *val)
{
- u64 val;
+ u64 msr_val;

/*
* As per the SDM, when IA32_QM_EVTSEL.EvtID (bits 7:0) is configured
@@ -180,14 +180,24 @@ static u64 __rmid_read(u32 rmid, enum resctrl_event_id eventid)
* are error bits.
*/
wrmsr(MSR_IA32_QM_EVTSEL, eventid, rmid);
- rdmsrl(MSR_IA32_QM_CTR, val);
+ rdmsrl(MSR_IA32_QM_CTR, msr_val);

- return val;
+ if (msr_val & RMID_VAL_ERROR)
+ return -EIO;
+ if (msr_val & RMID_VAL_UNAVAIL)
+ return -EINVAL;
+
+ *val = msr_val;
+
+ return 0;
}

static bool rmid_dirty(struct rmid_entry *entry)
{
- u64 val = __rmid_read(entry->rmid, QOS_L3_OCCUP_EVENT_ID);
+ u64 val = 0;
+
+ if (resctrl_arch_rmid_read(entry->rmid, QOS_L3_OCCUP_EVENT_ID, &val))
+ return true;

return val >= resctrl_cqm_threshold;
}
@@ -259,8 +269,8 @@ static void add_rmid_to_limbo(struct rmid_entry *entry)
{
struct rdt_resource *r;
struct rdt_domain *d;
- int cpu;
- u64 val;
+ int cpu, err;
+ u64 val = 0;

r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;

@@ -268,8 +278,10 @@ static void add_rmid_to_limbo(struct rmid_entry *entry)
cpu = get_cpu();
list_for_each_entry(d, &r->domains, list) {
if (cpumask_test_cpu(cpu, &d->cpu_mask)) {
- val = __rmid_read(entry->rmid, QOS_L3_OCCUP_EVENT_ID);
- if (val <= resctrl_cqm_threshold)
+ err = resctrl_arch_rmid_read(entry->rmid,
+ QOS_L3_OCCUP_EVENT_ID,
+ &val);
+ if (err || val <= resctrl_cqm_threshold)
continue;
}

@@ -315,19 +327,19 @@ static u64 mbm_overflow_count(u64 prev_msr, u64 cur_msr, unsigned int width)
return chunks >> shift;
}

-static u64 __mon_event_count(u32 rmid, struct rmid_read *rr)
+static int __mon_event_count(u32 rmid, struct rmid_read *rr)
{
struct rdt_hw_resource *hw_res = resctrl_to_arch_res(rr->r);
struct mbm_state *m;
- u64 chunks, tval;
+ u64 chunks, tval = 0;

if (rr->first)
resctrl_arch_reset_rmid(rr->r, rr->d, rmid, rr->evtid);

- tval = __rmid_read(rmid, rr->evtid);
- if (tval & (RMID_VAL_ERROR | RMID_VAL_UNAVAIL)) {
- return tval;
- }
+ rr->err = resctrl_arch_rmid_read(rmid, rr->evtid, &tval);
+ if (rr->err)
+ return rr->err;
+
switch (rr->evtid) {
case QOS_L3_OCCUP_EVENT_ID:
rr->val += tval;
@@ -341,9 +353,9 @@ static u64 __mon_event_count(u32 rmid, struct rmid_read *rr)
default:
/*
* Code would never reach here because an invalid
- * event id would fail the __rmid_read.
+ * event id would fail in resctrl_arch_rmid_read().
*/
- return RMID_VAL_ERROR;
+ return -EINVAL;
}

if (rr->first) {
@@ -399,11 +411,11 @@ void mon_event_count(void *info)
struct rdtgroup *rdtgrp, *entry;
struct rmid_read *rr = info;
struct list_head *head;
- u64 ret_val;
+ int ret;

rdtgrp = rr->rgrp;

- ret_val = __mon_event_count(rdtgrp->mon.rmid, rr);
+ ret = __mon_event_count(rdtgrp->mon.rmid, rr);

/*
* For Ctrl groups read data from child monitor groups and
@@ -415,13 +427,17 @@ void mon_event_count(void *info)
if (rdtgrp->type == RDTCTRL_GROUP) {
list_for_each_entry(entry, head, mon.crdtgrp_list) {
if (__mon_event_count(entry->mon.rmid, rr) == 0)
- ret_val = 0;
+ ret = 0;
}
}

- /* Report error if none of rmid_reads are successful */
- if (ret_val)
- rr->val = ret_val;
+ /*
+ * __mon_event_count() calls for newly created monitor groups may
+ * report -EINVAL/Unavailable if the monitor hasn't seen any traffic.
+ * Discard error if any of the monitor event reads succeeded.
+ */
+ if (ret == 0)
+ rr->err = 0;
}

/*
diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
index 8184567..efe60dd 100644
--- a/include/linux/resctrl.h
+++ b/include/linux/resctrl.h
@@ -219,6 +219,7 @@ u32 resctrl_arch_get_config(struct rdt_resource *r, struct rdt_domain *d,
u32 closid, enum resctrl_conf_type type);
int resctrl_online_domain(struct rdt_resource *r, struct rdt_domain *d);
void resctrl_offline_domain(struct rdt_resource *r, struct rdt_domain *d);
+int resctrl_arch_rmid_read(u32 rmid, enum resctrl_event_id eventid, u64 *res);

/**
* resctrl_arch_reset_rmid() - Reset any private state associated with rmid

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