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Message-Id: <20230113175459.14825-10-james.morse@arm.com>
Date: Fri, 13 Jan 2023 17:54:50 +0000
From: James Morse <james.morse@....com>
To: x86@...nel.org, linux-kernel@...r.kernel.org
Cc: Fenghua Yu <fenghua.yu@...el.com>,
Reinette Chatre <reinette.chatre@...el.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
H Peter Anvin <hpa@...or.com>,
Babu Moger <Babu.Moger@....com>,
James Morse <james.morse@....com>,
shameerali.kolothum.thodi@...wei.com,
D Scott Phillips OS <scott@...amperecomputing.com>,
carl@...amperecomputing.com, lcherian@...vell.com,
bobo.shaobowang@...wei.com, tan.shaopeng@...itsu.com,
xingxin.hx@...nanolis.org, baolin.wang@...ux.alibaba.com,
Jamie Iles <quic_jiles@...cinc.com>,
Xin Hao <xhao@...ux.alibaba.com>, peternewman@...gle.com
Subject: [PATCH v2 09/18] x86/resctrl: Allow resctrl_arch_rmid_read() to sleep
MPAM's cache occupancy counters can take a little while to settle once
the monitor has been configured. The maximum settling time is described
to the driver via a firmware table. The value could be large enough
that it makes sense to sleep.
To avoid exposing this to resctrl, it should be hidden behind MPAM's
resctrl_arch_rmid_read(). But add_rmid_to_limbo() calls
resctrl_arch_rmid_read() from a non-preemptible context.
add_rmid_to_limbo() is opportunistically reading the L3 occupancy counter
on this domain to avoid adding the RMID to limbo if this domain's value
has drifted below resctrl_rmid_realloc_threshold since the limbo handler
last ran. Determining 'this domain' involves disabling preeption to
prevent the thread being migrated to CPUs in a different domain between
the check and resctrl_arch_rmid_read() call. The check is skipped
for all remote domains.
Instead, call resctrl_arch_rmid_read() for each domain, and get it to
read the arch specific counter via IPI if its called on a CPU outside
the target domain. By covering remote domains, this change stops the
limbo handler from being started unnecessarily.
This also allows resctrl_arch_rmid_read() to sleep.
Tested-by: Shaopeng Tan <tan.shaopeng@...itsu.com>
Signed-off-by: James Morse <james.morse@....com>
---
The alternative is to remove the counter read from this path altogether,
and assume user-space would never try to re-allocate the last RMID before
the limbo handler runs next.
---
arch/x86/kernel/cpu/resctrl/monitor.c | 58 ++++++++++++++++++---------
1 file changed, 38 insertions(+), 20 deletions(-)
diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
index d309b830aeb2..d6ae4b713801 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -206,17 +206,19 @@ static u64 mbm_overflow_count(u64 prev_msr, u64 cur_msr, unsigned int width)
return chunks >> shift;
}
-int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_domain *d,
- u32 closid, u32 rmid, enum resctrl_event_id eventid,
- u64 *val)
+struct __rmid_read_arg
{
- struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
- struct rdt_hw_domain *hw_dom = resctrl_to_arch_dom(d);
- struct arch_mbm_state *am;
- u64 msr_val, chunks;
+ u32 rmid;
+ enum resctrl_event_id eventid;
- if (!cpumask_test_cpu(smp_processor_id(), &d->cpu_mask))
- return -EINVAL;
+ u64 msr_val;
+};
+
+static void __rmid_read(void *arg)
+{
+ enum resctrl_event_id eventid = ((struct __rmid_read_arg *)arg)->eventid;
+ u32 rmid = ((struct __rmid_read_arg *)arg)->rmid;
+ u64 msr_val;
/*
* As per the SDM, when IA32_QM_EVTSEL.EvtID (bits 7:0) is configured
@@ -229,6 +231,28 @@ int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_domain *d,
wrmsr(MSR_IA32_QM_EVTSEL, eventid, rmid);
rdmsrl(MSR_IA32_QM_CTR, msr_val);
+ ((struct __rmid_read_arg *)arg)->msr_val = msr_val;
+}
+
+int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_domain *d,
+ u32 closid, u32 rmid, enum resctrl_event_id eventid,
+ u64 *val)
+{
+ struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
+ struct rdt_hw_domain *hw_dom = resctrl_to_arch_dom(d);
+ struct __rmid_read_arg arg;
+ struct arch_mbm_state *am;
+ u64 msr_val, chunks;
+ int err;
+
+ arg.rmid = rmid;
+ arg.eventid = eventid;
+
+ err = smp_call_function_any(&d->cpu_mask, __rmid_read, &arg, true);
+ if (err)
+ return err;
+
+ msr_val = arg.msr_val;
if (msr_val & RMID_VAL_ERROR)
return -EIO;
if (msr_val & RMID_VAL_UNAVAIL)
@@ -383,23 +407,18 @@ static void add_rmid_to_limbo(struct rmid_entry *entry)
{
struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
struct rdt_domain *d;
- int cpu, err;
u64 val = 0;
u32 idx;
+ int err;
idx = resctrl_arch_rmid_idx_encode(entry->closid, entry->rmid);
entry->busy = 0;
- cpu = get_cpu();
list_for_each_entry(d, &r->domains, list) {
- if (cpumask_test_cpu(cpu, &d->cpu_mask)) {
- err = resctrl_arch_rmid_read(r, d, entry->closid,
- entry->rmid,
- QOS_L3_OCCUP_EVENT_ID,
- &val);
- if (err || val <= resctrl_rmid_realloc_threshold)
- continue;
- }
+ err = resctrl_arch_rmid_read(r, d, entry->closid, entry->rmid,
+ QOS_L3_OCCUP_EVENT_ID, &val);
+ if (err || val <= resctrl_rmid_realloc_threshold)
+ continue;
/*
* For the first limbo RMID in the domain,
@@ -410,7 +429,6 @@ static void add_rmid_to_limbo(struct rmid_entry *entry)
set_bit(idx, d->rmid_busy_llc);
entry->busy++;
}
- put_cpu();
if (entry->busy)
rmid_limbo_count++;
--
2.30.2
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