Add hooks for every mount/unmount of the resctrl file system so that
architecture code can allocate on mount and free on unmount.

Signed-off-by: Tony Luck <tony.luck@intel.com>
---
 include/linux/resctrl.h                 | 11 +++++++++--
 arch/x86/kernel/cpu/resctrl/internal.h  |  8 ++++++--
 arch/x86/kernel/cpu/resctrl/core.c      | 14 +++++++++++++-
 arch/x86/kernel/cpu/resctrl/intel_aet.c | 13 +++++++++++++
 fs/resctrl/rdtgroup.c                   | 20 ++++++++++++++++----
 5 files changed, 57 insertions(+), 9 deletions(-)

diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
index b312aaf76974..fd16256d01a7 100644
--- a/include/linux/resctrl.h
+++ b/include/linux/resctrl.h
@@ -518,11 +518,18 @@ void resctrl_online_cpu(unsigned int cpu);
 void resctrl_offline_cpu(unsigned int cpu);
 
 /*
- * Architecture hook called at beginning of first file system mount attempt.
- * No locks are held.
+ * Architecture hooks for resctrl mount/unmount. No locks are held.
  */
+
+/* Called at beginning of each file system mount attempt. */
 void resctrl_arch_pre_mount(void);
 
+/* Called to report success/failure of mount. */
+void resctrl_arch_mount_result(int ret);
+
+/* Called to report unmount. */
+void resctrl_arch_unmount(void);
+
 /**
  * resctrl_arch_rmid_read() - Read the eventid counter corresponding to rmid
  *			      for this resource and domain.
diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index e3cfa0c10e92..6f322818a9e6 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -234,14 +234,18 @@ void rdt_domain_reconfigure_cdp(struct rdt_resource *r);
 void resctrl_arch_mbm_cntr_assign_set_one(struct rdt_resource *r);
 
 #ifdef CONFIG_X86_CPU_RESCTRL_INTEL_AET
-bool intel_aet_get_events(void);
+bool intel_aet_pre_mount(void);
+void intel_aet_mount_result(int ret);
+void intel_aet_unmount(void);
 void __exit intel_aet_exit(void);
 int intel_aet_read_event(int domid, u32 rmid, void *arch_priv, u64 *val);
 void intel_aet_mon_domain_setup(int cpu, int id, struct rdt_resource *r,
 				struct list_head *add_pos);
 bool intel_handle_aet_option(bool force_off, char *tok);
 #else
-static inline bool intel_aet_get_events(void) { return false; }
+static inline bool intel_aet_pre_mount(void) { return false; }
+static inline void intel_aet_mount_result(int ret) { }
+static inline void intel_aet_unmount(void) { }
 static inline void __exit intel_aet_exit(void) { }
 static inline int intel_aet_read_event(int domid, u32 rmid, void *arch_priv, u64 *val)
 {
diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
index 7667cf7c4e94..162eca2cfcdb 100644
--- a/arch/x86/kernel/cpu/resctrl/core.c
+++ b/arch/x86/kernel/cpu/resctrl/core.c
@@ -769,8 +769,10 @@ void resctrl_arch_pre_mount(void)
 	struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_PERF_PKG].r_resctrl;
 	int cpu;
 
-	if (!intel_aet_get_events())
+	if (!intel_aet_pre_mount()) {
+		r->mon_capable = false;
 		return;
+	}
 
 	/*
 	 * Late discovery of telemetry events means the domains for the
@@ -786,6 +788,16 @@ void resctrl_arch_pre_mount(void)
 	cpus_read_unlock();
 }
 
+void resctrl_arch_mount_result(int ret)
+{
+	intel_aet_mount_result(ret);
+}
+
+void resctrl_arch_unmount(void)
+{
+	intel_aet_unmount();
+}
+
 enum {
 	RDT_FLAG_CMT,
 	RDT_FLAG_MBM_TOTAL,
diff --git a/arch/x86/kernel/cpu/resctrl/intel_aet.c b/arch/x86/kernel/cpu/resctrl/intel_aet.c
index 015627401ed2..743a1894fe9a 100644
--- a/arch/x86/kernel/cpu/resctrl/intel_aet.c
+++ b/arch/x86/kernel/cpu/resctrl/intel_aet.c
@@ -335,6 +335,19 @@ void __exit intel_aet_exit(void)
 	}
 }
 
+bool intel_aet_pre_mount(void)
+{
+	return false; // Temporary stub
+}
+
+void intel_aet_mount_result(int ret)
+{
+}
+
+void intel_aet_unmount(void)
+{
+}
+
 #define DATA_VALID	BIT_ULL(63)
 #define DATA_BITS	GENMASK_ULL(62, 0)
 
diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index 5da305bd36c9..edcee79de424 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -18,7 +18,6 @@
 #include <linux/fs_parser.h>
 #include <linux/sysfs.h>
 #include <linux/kernfs.h>
-#include <linux/once.h>
 #include <linux/resctrl.h>
 #include <linux/seq_buf.h>
 #include <linux/seq_file.h>
@@ -2788,8 +2787,6 @@ static int rdt_get_tree(struct fs_context *fc)
 	struct rdt_resource *r;
 	int ret;
 
-	DO_ONCE_SLEEPABLE(resctrl_arch_pre_mount);
-
 	cpus_read_lock();
 	mutex_lock(&rdtgroup_mutex);
 	/*
@@ -2900,6 +2897,19 @@ static int rdt_get_tree(struct fs_context *fc)
 	return ret;
 }
 
+static int rdt_get_tree_wrapper(struct fs_context *fc)
+{
+	int ret;
+
+	resctrl_arch_pre_mount();
+
+	ret = rdt_get_tree(fc);
+
+	resctrl_arch_mount_result(ret);
+
+	return ret;
+}
+
 enum rdt_param {
 	Opt_cdp,
 	Opt_cdpl2,
@@ -2959,7 +2969,7 @@ static void rdt_fs_context_free(struct fs_context *fc)
 static const struct fs_context_operations rdt_fs_context_ops = {
 	.free		= rdt_fs_context_free,
 	.parse_param	= rdt_parse_param,
-	.get_tree	= rdt_get_tree,
+	.get_tree	= rdt_get_tree_wrapper,
 };
 
 static int rdt_init_fs_context(struct fs_context *fc)
@@ -3187,6 +3197,8 @@ static void rdt_kill_sb(struct super_block *sb)
 	kernfs_kill_sb(sb);
 	mutex_unlock(&rdtgroup_mutex);
 	cpus_read_unlock();
+
+	resctrl_arch_unmount();
 }
 
 static struct file_system_type rdt_fs_type = {
-- 
2.53.0

Hi Tony,

On 3/28/2026 7:02 AM, Tony Luck wrote:

> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
> index e3cfa0c10e92..6f322818a9e6 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -234,14 +234,18 @@ void rdt_domain_reconfigure_cdp(struct rdt_resource *r);
>   void resctrl_arch_mbm_cntr_assign_set_one(struct rdt_resource *r);
>   
>   #ifdef CONFIG_X86_CPU_RESCTRL_INTEL_AET
> -bool intel_aet_get_events(void);
> +bool intel_aet_pre_mount(void);
> +void intel_aet_mount_result(int ret);
> +void intel_aet_unmount(void);
>   void __exit intel_aet_exit(void);
>   int intel_aet_read_event(int domid, u32 rmid, void *arch_priv, u64 *val);
>   void intel_aet_mon_domain_setup(int cpu, int id, struct rdt_resource *r,
>   				struct list_head *add_pos);
>   bool intel_handle_aet_option(bool force_off, char *tok);
>   #else
> -static inline bool intel_aet_get_events(void) { return false; }

The declaration of intel_aet_get_events() was removed,
and the function definition still remains in intel_aet.c.
Not sure if this will trigger a warning like
"no user for intel_aet_get_events". Since intel_aet_get_events() is
renamed to static get_events() in a subsequent patch,
perhaps we can mark intel_aet_get_events() as static in
this patch too?

thanks,
Chenyu

> > -static inline bool intel_aet_get_events(void) { return false; }
>
> The declaration of intel_aet_get_events() was removed,
> and the function definition still remains in intel_aet.c.
> Not sure if this will trigger a warning like
> "no user for intel_aet_get_events". Since intel_aet_get_events() is
> renamed to static get_events() in a subsequent patch,
> perhaps we can mark intel_aet_get_events() as static in
> this patch too?

I need to explain more in the commit message. Or find a better way to do this.

I wanted to split the file system changes from the architecture changes to make
review easier.  But doing the file system first means that architecture is now
called on every mount, and it isn't ready for that. So, I cheated by breaking
the enumeration of AET in this patch and fixing it in next patch. The kernel
build is ok, so anyone bisecting some other issue won't see a problem (other
than AET not enumerated).

-Tony