Commit 70288405 authored by James Morse's avatar James Morse Committed by Borislav Petkov (AMD)
Browse files

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: default avatarJames Morse <james.morse@arm.com>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: default avatarShaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Reviewed-by: default avatarTony Luck <tony.luck@intel.com>
Reviewed-by: default avatarReinette Chatre <reinette.chatre@intel.com>
Reviewed-by: default avatarFenghua Yu <fenghuay@nvidia.com>
Reviewed-by: default avatarBabu Moger <babu.moger@amd.com>
Tested-by: Carl Worth <carl@os.amperecomputing.com> # arm64
Tested-by: default avatarShaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Tested-by: default avatarPeter Newman <peternewman@google.com>
Tested-by: Amit Singh Tomar <amitsinght@marvell.com> # arm64
Tested-by: Shanker Donthineni <sdonthineni@nvidia.com> # arm64
Tested-by: default avatarBabu Moger <babu.moger@amd.com>
Link: https://lore.kernel.org/r/20250311183715.16445-25-james.morse@arm.com
parent 7d0ec14c

arch/x86/Kconfig

+7 −0
Original line number Diff line number Diff line
@@ -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

arch/x86/kernel/cpu/resctrl/Makefile

+3 −2
Original line number Diff line number Diff line 
# 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)		+= ctrlmondata.o

obj-$(CONFIG_RESCTRL_FS_PSEUDO_LOCK)	+= pseudo_lock.o

CFLAGS_pseudo_lock.o = -I$(src)

arch/x86/kernel/cpu/resctrl/internal.h

+41 −8
Original line number Diff line number Diff line
@@ -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 */

arch/x86/kernel/cpu/resctrl/rdtgroup.c

+2 −1
Original line number Diff line number Diff line
@@ -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;