[PATCH v5 24/41] arm_mpam: resctrl: Wait for cacheinfo to be ready

Ben Horgan
2026-02-24T17:59:39Z

In order to calculate the rmid realloc threshold the size of the cache
needs to be known. Cache domains will also be named after the cache id. So
that this information can be extracted from cacheinfo we need to wait for
it to be ready. The cacheinfo information is populated in device_initcall()
so we wait for that.

Tested-by: Gavin Shan <gshan@redhat.com>
Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Tested-by: Peter Newman <peternewman@google.com>
Tested-by: Zeng Heng <zengheng4@huawei.com>
Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Signed-off-by: James Morse <james.morse@arm.com>
[horgan: split out from another patch]
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
This is moved into it's own patch to allow all uses of cacheinfo to be
valid when they are introduced.
---
drivers/resctrl/mpam_resctrl.c | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)

diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index 48f96d7f9109..fc5877eb5970 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -16,6 +16,7 @@
#include <linux/resctrl.h>
#include <linux/slab.h>
#include <linux/types.h>
+#include <linux/wait.h>

#include <asm/mpam.h>

@@ -42,6 +43,13 @@ static DEFINE_MUTEX(domain_list_lock);
*/
static bool cdp_enabled;

+/*
+ * We use cacheinfo to discover the size of the caches and their id. cacheinfo
+ * populates this from a device_initcall(). mpam_resctrl_setup() must wait.
+ */
+static bool cacheinfo_ready;
+static DECLARE_WAIT_QUEUE_HEAD(wait_cacheinfo_ready);
+
bool resctrl_arch_alloc_capable(void)
{
struct mpam_resctrl_res *res;
@@ -743,6 +751,8 @@ int mpam_resctrl_setup(void)
struct mpam_resctrl_res *res;
enum resctrl_res_level rid;

+ wait_event(wait_cacheinfo_ready, cacheinfo_ready);
+
cpus_read_lock();
for_each_mpam_resctrl_control(res, rid) {
INIT_LIST_HEAD_RCU(&res->resctrl_res.ctrl_domains);
@@ -781,6 +791,15 @@ int mpam_resctrl_setup(void)
return 0;
}

+static int __init __cacheinfo_ready(void)
+{
+ cacheinfo_ready = true;
+ wake_up(&wait_cacheinfo_ready);
+
+ return 0;
+}
+device_initcall_sync(__cacheinfo_ready);
+
#ifdef CONFIG_MPAM_KUNIT_TEST
#include "test_mpam_resctrl.c"
#endif
--
2.43.0