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@arm.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Fenghua Yu <fenghuay@nvidia.com>
Reviewed-by: Babu Moger <babu.moger@amd.com>
Tested-by: Carl Worth <carl@os.amperecomputing.com> # arm64
Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Tested-by: Peter Newman <peternewman@google.com>
Tested-by: Amit Singh Tomar <amitsinght@marvell.com> # arm64
Tested-by: Shanker Donthineni <sdonthineni@nvidia.com> # arm64
Tested-by: Babu Moger <babu.moger@amd.com>
Link: https://lore.kernel.org/r/20250311183715.16445-25-james.morse@arm.com

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 0e27ebd7e36a9e3d69ad3e77c8db5dcf11ae3016..3cb3acdbc1071fbe1e463aba8d61c001be8004d6 100644 (file)
--- 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 4a06c37b9cf11bef1b00b546e3c2344691e6e18a..0c13b0befd8a9b76fe4753b8ee230113e5f3bf54 100644 (file)
--- 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 725f223ea07be091b985b240835ce9ff8e8743f6..8d35bb423aaddfa78708171555f3ebf1ac88d8e4 100644 (file)
--- 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 a388ef66ef4ca56f9d199c829bed8fa7a152e6a2..e59271515a4634b0535b0cf41ecff28fb1c3bb74 100644 (file)
--- 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;