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Subject[PATCH v2] x86/resctrl: Preserve CDP enable over cpuhp
Date
Resctrl assumes that all CPUs are online when the filesystem is
mounted, and that CPUs remember their CDP-enabled state over CPU
hotplug.

This goes wrong when resctrl's CDP-enabled state changes while all
the CPUs in a domain are offline.

When a domain comes online, enable (or disable!) CDP to match resctrl's
current setting.

Fixes: 5ff193fbde20 ("x86/intel_rdt: Add basic resctrl filesystem support")
Suggested-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: James Morse <james.morse@arm.com>

---
Changes since v1:
* Explicitly test for L2/L3 resources to ignore duplicate calls.
* Poke the LxDATA resources to avoid confusing CDP-off with CDP-unsupported.
* Moved code to rdtgroup.c for fewer exported functions.

v1: lore.kernel.org/r/20200212185359.163111-1-james.morse@arm.com
---
arch/x86/kernel/cpu/resctrl/core.c | 2 ++
arch/x86/kernel/cpu/resctrl/internal.h | 1 +
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 18 ++++++++++++++++++
3 files changed, 21 insertions(+)

diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
index 89049b343c7a..d8cc5223b7ce 100644
--- a/arch/x86/kernel/cpu/resctrl/core.c
+++ b/arch/x86/kernel/cpu/resctrl/core.c
@@ -578,6 +578,8 @@ static void domain_add_cpu(int cpu, struct rdt_resource *r)
d->id = id;
cpumask_set_cpu(cpu, &d->cpu_mask);

+ rdt_domain_reconfigure_cdp(r);
+
if (r->alloc_capable && domain_setup_ctrlval(r, d)) {
kfree(d);
return;
diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index 181c992f448c..3dd13f3a8b23 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -601,5 +601,6 @@ bool has_busy_rmid(struct rdt_resource *r, struct rdt_domain *d);
void __check_limbo(struct rdt_domain *d, bool force_free);
bool cbm_validate_intel(char *buf, u32 *data, struct rdt_resource *r);
bool cbm_validate_amd(char *buf, u32 *data, struct rdt_resource *r);
+void rdt_domain_reconfigure_cdp(struct rdt_resource *r);

#endif /* _ASM_X86_RESCTRL_INTERNAL_H */
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 064e9ef44cd6..5967320a1951 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -1831,6 +1831,9 @@ static int set_cache_qos_cfg(int level, bool enable)
struct rdt_domain *d;
int cpu;

+ /* CDP state is restored during cpuhp, which takes this lock */
+ lockdep_assert_held(&rdtgroup_mutex);
+
if (level == RDT_RESOURCE_L3)
update = l3_qos_cfg_update;
else if (level == RDT_RESOURCE_L2)
@@ -1859,6 +1862,21 @@ static int set_cache_qos_cfg(int level, bool enable)
return 0;
}

+/* Restore the qos cfg state when a package comes online */
+void rdt_domain_reconfigure_cdp(struct rdt_resource *r)
+{
+ lockdep_assert_held(&rdtgroup_mutex);
+
+ if (!r->alloc_capable)
+ return;
+
+ if (r == &rdt_resources_all[RDT_RESOURCE_L2DATA])
+ l2_qos_cfg_update(&r->alloc_enabled);
+
+ if (r == &rdt_resources_all[RDT_RESOURCE_L3DATA])
+ l3_qos_cfg_update(&r->alloc_enabled);
+}
+
/*
* Enable or disable the MBA software controller
* which helps user specify bandwidth in MBps.
--
2.24.1
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