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Date: Fri, 26 Apr 2024 16:08:33 +0100
From: Dave Martin <Dave.Martin@....com>
To: x86@...nel.org,
linux-kernel@...r.kernel.org
Cc: James Morse <james.morse@....com>,
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>,
shameerali.kolothum.thodi@...wei.com,
D Scott Phillips OS <scott@...amperecomputing.com>,
carl@...amperecomputing.com,
lcherian@...vell.com,
bobo.shaobowang@...wei.com,
"Shaopeng Tan (Fujitsu)" <tan.shaopeng@...itsu.com>,
baolin.wang@...ux.alibaba.com,
Jamie Iles <quic_jiles@...cinc.com>,
Xin Hao <xhao@...ux.alibaba.com>,
Peter Newman <peternewman@...gle.com>,
dfustini@...libre.com,
amitsinght@...vell.com,
David Hildenbrand <david@...hat.com>,
Rex Nie <rex.nie@...uarmicro.com>
Subject: [PATCH v2 04/35] x86/resctrl: Add helper for setting CPU default properties
From: James Morse <james.morse@....com>
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@....com>
Signed-off-by: Dave Martin <Dave.Martin@....com>
---
Changes in v2:
* In rdtgroup_rmdir_mon(), (re)set CPU default closid based on the
parent control group, to avoid the appearance of referencing
something that we're in the process of destroying (even if it
doesn't make a difference because the victim mon group necessarily
has the same closid as the parent control group).
Update comment to match.
No (intentional) functional change.
---
arch/x86/include/asm/resctrl.h | 14 +++++++++++---
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 20 ++++++++++++++------
2 files changed, 25 insertions(+), 9 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 47234562a1dd..98c051ac848d 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -3624,14 +3624,21 @@ 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 */
+ /*
+ * Update per cpu closid/rmid of the moved CPUs first.
+ * Note: the closid will not change, but the arch code still needs it.
+ */
+ closid = prdtgrp->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.
@@ -3664,6 +3671,7 @@ 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 */
@@ -3674,10 +3682,10 @@ 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
--
2.34.1
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