[PATCH v6 08/21] x86/resctrl: Create mba_sc configuration in the rdt_domain

James Morse
2022-09-02T15:55:57Z

To support resctrl's MBA software controller, the architecture must provide
a second configuration array to hold the mbps_val[] from user-space.

This complicates the interface between the architecture specific code and
the filesystem portions of resctrl that will move to /fs/, to allow
multiple architectures to support resctrl.

Make the filesystem parts of resctrl create an array for the mba_sc
values. The software controller can be changed to use this, allowing
the architecture code to only consider the values configured in hardware.

Reviewed-by: Jamie Iles <quic_jiles@quicinc.com>
Tested-by: Xin Hao <xhao@linux.alibaba.com>
Reviewed-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Tested-by: Cristian Marussi <cristian.marussi@arm.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: James Morse <james.morse@arm.com>
---
Changes since v4:
* Use supports_mba_mbps() in resctrl_{on,off}line_domain().
* Don't call mba_sc_domain_destroy() for error handling - it can't happen.
* Whitespace.

Changes since v3:
* Always allocate the array.
* Move the array allocation above the r->mon_capable check.

Changes since v2:
* Split patch in two, the liftime parts are a separate patch.
* Added reset in set_mba_sc() now that we can't depend on the lifetime.
* Initialise ret in mba_sc_allocate(),
* Made mbps_val allocation/freeing symmetric for cpuhp calls.
* Removed reference to squashed-out struct.
* Preserved kerneldoc for mbps_val.

Changes since v1:
* Added missing error handling to mba_sc_domain_allocate() in
domain_setup_mon_state()
* Added comment about mba_sc_domain_allocate() races
* Squashed out struct resctrl_mba_sc
* Moved mount time alloc/free calls to set_mba_sc().
* Removed mount check in resctrl_offline_domain()
* Reword commit message
---
arch/x86/kernel/cpu/resctrl/internal.h | 1 -
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 39 ++++++++++++++++++++++++++
include/linux/resctrl.h | 7 +++++
3 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index e12b55f815bf..a7e2cbce29d5 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -36,7 +36,6 @@
#define MBM_OVERFLOW_INTERVAL 1000
#define MAX_MBA_BW 100u
#define MBA_IS_LINEAR 0x4
-#define MBA_MAX_MBPS U32_MAX
#define MAX_MBA_BW_AMD 0x800
#define MBM_CNTR_WIDTH_OFFSET_AMD 20

diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 4ee26264ecfc..f7ebd019e7a5 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -1889,6 +1889,30 @@ void rdt_domain_reconfigure_cdp(struct rdt_resource *r)
l3_qos_cfg_update(&hw_res->cdp_enabled);
}

+static int mba_sc_domain_allocate(struct rdt_resource *r, struct rdt_domain *d)
+{
+ u32 num_closid = resctrl_arch_get_num_closid(r);
+ int cpu = cpumask_any(&d->cpu_mask);
+ int i;
+
+ d->mbps_val = kcalloc_node(num_closid, sizeof(*d->mbps_val),
+ GFP_KERNEL, cpu_to_node(cpu));
+ if (!d->mbps_val)
+ return -ENOMEM;
+
+ for (i = 0; i < num_closid; i++)
+ d->mbps_val[i] = MBA_MAX_MBPS;
+
+ return 0;
+}
+
+static void mba_sc_domain_destroy(struct rdt_resource *r,
+ struct rdt_domain *d)
+{
+ kfree(d->mbps_val);
+ d->mbps_val = NULL;
+}
+
/*
* MBA software controller is supported only if
* MBM is supported and MBA is in linear scale.
@@ -1908,12 +1932,20 @@ static bool supports_mba_mbps(void)
static int set_mba_sc(bool mba_sc)
{
struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_MBA].r_resctrl;
+ u32 num_closid = resctrl_arch_get_num_closid(r);
+ struct rdt_domain *d;
+ int i;

if (!supports_mba_mbps() || mba_sc == is_mba_sc(r))
return -EINVAL;

r->membw.mba_sc = mba_sc;

+ list_for_each_entry(d, &r->domains, list) {
+ for (i = 0; i < num_closid; i++)
+ d->mbps_val[i] = MBA_MAX_MBPS;
+ }
+
return 0;
}

@@ -3247,6 +3279,9 @@ void resctrl_offline_domain(struct rdt_resource *r, struct rdt_domain *d)
{
lockdep_assert_held(&rdtgroup_mutex);

+ if (supports_mba_mbps() && r->rid == RDT_RESOURCE_MBA)
+ mba_sc_domain_destroy(r, d);
+
if (!r->mon_capable)
return;

@@ -3311,6 +3346,10 @@ int resctrl_online_domain(struct rdt_resource *r, struct rdt_domain *d)

lockdep_assert_held(&rdtgroup_mutex);

+ if (supports_mba_mbps() && r->rid == RDT_RESOURCE_MBA)
+ /* RDT_RESOURCE_MBA is never mon_capable */
+ return mba_sc_domain_allocate(r, d);
+
if (!r->mon_capable)
return 0;

diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
index 5d283bdd6162..93dfe553b364 100644
--- a/include/linux/resctrl.h
+++ b/include/linux/resctrl.h
@@ -15,6 +15,9 @@ int proc_resctrl_show(struct seq_file *m,

#endif

+/* max value for struct rdt_domain's mbps_val */
+#define MBA_MAX_MBPS U32_MAX
+
/**
* enum resctrl_conf_type - The type of configuration.
* @CDP_NONE: No prioritisation, both code and data are controlled or monitored.
@@ -53,6 +56,9 @@ struct resctrl_staged_config {
* @cqm_work_cpu: worker CPU for CQM h/w counters
* @plr: pseudo-locked region (if any) associated with domain
* @staged_config: parsed configuration to be applied
+ * @mbps_val: When mba_sc is enabled, this holds the array of user
+ * specified control values for mba_sc in MBps, indexed
+ * by closid
*/
struct rdt_domain {
struct list_head list;
@@ -67,6 +73,7 @@ struct rdt_domain {
int cqm_work_cpu;
struct pseudo_lock_region *plr;
struct resctrl_staged_config staged_config[CDP_NUM_TYPES];
+ u32 *mbps_val;
};

/**
--
2.30.2