[tip: x86/cache] x86/resctrl: Allow an architecture to disable pseudo lock
From: tip-bot2 for James Morse
Date: Wed Mar 12 2025 - 13:21:44 EST
The following commit has been merged into the x86/cache branch of tip:
Commit-ID: 7028840552a220ac5efe51a4b554195cd954a912
Gitweb: https://git.kernel.org/tip/7028840552a220ac5efe51a4b554195cd954a912
Author: James Morse <james.morse@xxxxxxx>
AuthorDate: Tue, 11 Mar 2025 18:37:09
Committer: Borislav Petkov (AMD) <bp@xxxxxxxxx>
CommitterDate: Wed, 12 Mar 2025 12:24:25 +01:00
x86/resctrl: Allow an architecture to disable pseudo lock
Pseudo-lock relies on knowledge of the micro-architecture to disable
prefetchers etc.
On arm64 these controls are typically secure only, meaning Linux can't access
them. Arm's cache-lockdown feature works in a very different way. Resctrl's
pseudo-lock isn't going to be used on arm64 platforms.
Add a Kconfig symbol that can be selected by the architecture. This enables or
disables building of the pseudo_lock.c file, and replaces the functions with
stubs. An additional IS_ENABLED() check is needed in rdtgroup_mode_write() so
that attempting to enable pseudo-lock reports an "Unknown or unsupported mode"
to user-space via the last_cmd_status file.
Signed-off-by: James Morse <james.morse@xxxxxxx>
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Reviewed-by: Shaopeng Tan <tan.shaopeng@xxxxxxxxxxxxxx>
Reviewed-by: Tony Luck <tony.luck@xxxxxxxxx>
Reviewed-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
Reviewed-by: Fenghua Yu <fenghuay@xxxxxxxxxx>
Reviewed-by: Babu Moger <babu.moger@xxxxxxx>
Tested-by: Carl Worth <carl@xxxxxxxxxxxxxxxxxxxxxx> # arm64
Tested-by: Shaopeng Tan <tan.shaopeng@xxxxxxxxxxxxxx>
Tested-by: Peter Newman <peternewman@xxxxxxxxxx>
Tested-by: Amit Singh Tomar <amitsinght@xxxxxxxxxxx> # arm64
Tested-by: Shanker Donthineni <sdonthineni@xxxxxxxxxx> # arm64
Tested-by: Babu Moger <babu.moger@xxxxxxx>
Link: https://lore.kernel.org/r/20250311183715.16445-25-james.morse@xxxxxxx
---
arch/x86/Kconfig | 7 ++++-
arch/x86/kernel/cpu/resctrl/Makefile | 5 +--
arch/x86/kernel/cpu/resctrl/internal.h | 49 ++++++++++++++++++++-----
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 3 +-
4 files changed, 53 insertions(+), 11 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 0e27ebd..3cb3acd 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -505,6 +505,7 @@ config X86_CPU_RESCTRL
depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
select KERNFS
select PROC_CPU_RESCTRL if PROC_FS
+ select RESCTRL_FS_PSEUDO_LOCK
help
Enable x86 CPU resource control support.
@@ -521,6 +522,12 @@ config X86_CPU_RESCTRL
Say N if unsure.
+config RESCTRL_FS_PSEUDO_LOCK
+ bool
+ help
+ Software mechanism to pin data in a cache portion using
+ micro-architecture specific knowledge.
+
config X86_FRED
bool "Flexible Return and Event Delivery"
depends on X86_64
diff --git a/arch/x86/kernel/cpu/resctrl/Makefile b/arch/x86/kernel/cpu/resctrl/Makefile
index 4a06c37..0c13b0b 100644
--- a/arch/x86/kernel/cpu/resctrl/Makefile
+++ b/arch/x86/kernel/cpu/resctrl/Makefile
@@ -1,4 +1,5 @@
# SPDX-License-Identifier: GPL-2.0
-obj-$(CONFIG_X86_CPU_RESCTRL) += core.o rdtgroup.o monitor.o
-obj-$(CONFIG_X86_CPU_RESCTRL) += ctrlmondata.o pseudo_lock.o
+obj-$(CONFIG_X86_CPU_RESCTRL) += core.o rdtgroup.o monitor.o
+obj-$(CONFIG_X86_CPU_RESCTRL) += ctrlmondata.o
+obj-$(CONFIG_RESCTRL_FS_PSEUDO_LOCK) += pseudo_lock.o
CFLAGS_pseudo_lock.o = -I$(src)
diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index 725f223..8d35bb4 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -512,14 +512,6 @@ unsigned int rdtgroup_cbm_to_size(struct rdt_resource *r, struct rdt_ctrl_domain
unsigned long cbm);
enum rdtgrp_mode rdtgroup_mode_by_closid(int closid);
int rdtgroup_tasks_assigned(struct rdtgroup *r);
-int rdtgroup_locksetup_enter(struct rdtgroup *rdtgrp);
-int rdtgroup_locksetup_exit(struct rdtgroup *rdtgrp);
-bool rdtgroup_cbm_overlaps_pseudo_locked(struct rdt_ctrl_domain *d, unsigned long cbm);
-bool rdtgroup_pseudo_locked_in_hierarchy(struct rdt_ctrl_domain *d);
-int rdt_pseudo_lock_init(void);
-void rdt_pseudo_lock_release(void);
-int rdtgroup_pseudo_lock_create(struct rdtgroup *rdtgrp);
-void rdtgroup_pseudo_lock_remove(struct rdtgroup *rdtgrp);
struct rdt_ctrl_domain *get_ctrl_domain_from_cpu(int cpu, struct rdt_resource *r);
struct rdt_mon_domain *get_mon_domain_from_cpu(int cpu, struct rdt_resource *r);
int closids_supported(void);
@@ -551,4 +543,45 @@ void resctrl_file_fflags_init(const char *config, unsigned long fflags);
void rdt_staged_configs_clear(void);
bool closid_allocated(unsigned int closid);
int resctrl_find_cleanest_closid(void);
+
+#ifdef CONFIG_RESCTRL_FS_PSEUDO_LOCK
+int rdtgroup_locksetup_enter(struct rdtgroup *rdtgrp);
+int rdtgroup_locksetup_exit(struct rdtgroup *rdtgrp);
+bool rdtgroup_cbm_overlaps_pseudo_locked(struct rdt_ctrl_domain *d, unsigned long cbm);
+bool rdtgroup_pseudo_locked_in_hierarchy(struct rdt_ctrl_domain *d);
+int rdt_pseudo_lock_init(void);
+void rdt_pseudo_lock_release(void);
+int rdtgroup_pseudo_lock_create(struct rdtgroup *rdtgrp);
+void rdtgroup_pseudo_lock_remove(struct rdtgroup *rdtgrp);
+#else
+static inline int rdtgroup_locksetup_enter(struct rdtgroup *rdtgrp)
+{
+ return -EOPNOTSUPP;
+}
+
+static inline int rdtgroup_locksetup_exit(struct rdtgroup *rdtgrp)
+{
+ return -EOPNOTSUPP;
+}
+
+static inline bool rdtgroup_cbm_overlaps_pseudo_locked(struct rdt_ctrl_domain *d, unsigned long cbm)
+{
+ return false;
+}
+
+static inline bool rdtgroup_pseudo_locked_in_hierarchy(struct rdt_ctrl_domain *d)
+{
+ return false;
+}
+
+static inline int rdt_pseudo_lock_init(void) { return 0; }
+static inline void rdt_pseudo_lock_release(void) { }
+static inline int rdtgroup_pseudo_lock_create(struct rdtgroup *rdtgrp)
+{
+ return -EOPNOTSUPP;
+}
+
+static inline void rdtgroup_pseudo_lock_remove(struct rdtgroup *rdtgrp) { }
+#endif /* CONFIG_RESCTRL_FS_PSEUDO_LOCK */
+
#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 a388ef6..e592715 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -1453,7 +1453,8 @@ static ssize_t rdtgroup_mode_write(struct kernfs_open_file *of,
goto out;
}
rdtgrp->mode = RDT_MODE_EXCLUSIVE;
- } else if (!strcmp(buf, "pseudo-locksetup")) {
+ } else if (IS_ENABLED(CONFIG_RESCTRL_FS_PSEUDO_LOCK) &&
+ !strcmp(buf, "pseudo-locksetup")) {
ret = rdtgroup_locksetup_enter(rdtgrp);
if (ret)
goto out;