diff options
| -rw-r--r-- | arch/arm64/Kconfig | 2 | ||||
| -rw-r--r-- | arch/arm64/include/asm/mpam.h | 67 | ||||
| -rw-r--r-- | arch/arm64/include/asm/thread_info.h | 3 | ||||
| -rw-r--r-- | arch/arm64/kernel/Makefile | 1 | ||||
| -rw-r--r-- | arch/arm64/kernel/mpam.c | 13 | ||||
| -rw-r--r-- | arch/arm64/kernel/process.c | 7 | ||||
| -rw-r--r-- | drivers/resctrl/mpam_devices.c | 2 | ||||
| -rw-r--r-- | drivers/resctrl/mpam_internal.h | 4 |
8 files changed, 95 insertions, 4 deletions
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 38dba5f7e4d2..ecaaca13a969 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -2039,6 +2039,8 @@ config ARM64_MPAM MPAM is exposed to user-space via the resctrl pseudo filesystem. + This option enables the extra context switch code. + endmenu # "ARMv8.4 architectural features" menu "ARMv8.5 architectural features" diff --git a/arch/arm64/include/asm/mpam.h b/arch/arm64/include/asm/mpam.h new file mode 100644 index 000000000000..0747e0526927 --- /dev/null +++ b/arch/arm64/include/asm/mpam.h @@ -0,0 +1,67 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* Copyright (C) 2025 Arm Ltd. */ + +#ifndef __ASM__MPAM_H +#define __ASM__MPAM_H + +#include <linux/jump_label.h> +#include <linux/percpu.h> +#include <linux/sched.h> + +#include <asm/sysreg.h> + +DECLARE_STATIC_KEY_FALSE(mpam_enabled); +DECLARE_PER_CPU(u64, arm64_mpam_default); +DECLARE_PER_CPU(u64, arm64_mpam_current); + +/* + * The value of the MPAM0_EL1 sysreg when a task is in resctrl's default group. + * This is used by the context switch code to use the resctrl CPU property + * instead. The value is modified when CDP is enabled/disabled by mounting + * the resctrl filesystem. + */ +extern u64 arm64_mpam_global_default; + +/* + * The resctrl filesystem writes to the partid/pmg values for threads and CPUs, + * which may race with reads in mpam_thread_switch(). Ensure only one of the old + * or new values are used. Particular care should be taken with the pmg field as + * mpam_thread_switch() may read a partid and pmg that don't match, causing this + * value to be stored with cache allocations, despite being considered 'free' by + * resctrl. + */ +#ifdef CONFIG_ARM64_MPAM +static inline u64 mpam_get_regval(struct task_struct *tsk) +{ + return READ_ONCE(task_thread_info(tsk)->mpam_partid_pmg); +} + +static inline void mpam_thread_switch(struct task_struct *tsk) +{ + u64 oldregval; + int cpu = smp_processor_id(); + u64 regval = mpam_get_regval(tsk); + + if (!static_branch_likely(&mpam_enabled)) + return; + + if (regval == READ_ONCE(arm64_mpam_global_default)) + regval = READ_ONCE(per_cpu(arm64_mpam_default, cpu)); + + oldregval = READ_ONCE(per_cpu(arm64_mpam_current, cpu)); + if (oldregval == regval) + return; + + write_sysreg_s(regval | MPAM1_EL1_MPAMEN, SYS_MPAM1_EL1); + isb(); + + /* Synchronising the EL0 write is left until the ERET to EL0 */ + write_sysreg_s(regval, SYS_MPAM0_EL1); + + WRITE_ONCE(per_cpu(arm64_mpam_current, cpu), regval); +} +#else +static inline void mpam_thread_switch(struct task_struct *tsk) {} +#endif /* CONFIG_ARM64_MPAM */ + +#endif /* __ASM__MPAM_H */ diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h index 7942478e4065..5d7fe3e153c8 100644 --- a/arch/arm64/include/asm/thread_info.h +++ b/arch/arm64/include/asm/thread_info.h @@ -42,6 +42,9 @@ struct thread_info { void *scs_base; void *scs_sp; #endif +#ifdef CONFIG_ARM64_MPAM + u64 mpam_partid_pmg; +#endif u32 cpu; }; diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile index 76f32e424065..15979f366519 100644 --- a/arch/arm64/kernel/Makefile +++ b/arch/arm64/kernel/Makefile @@ -67,6 +67,7 @@ obj-$(CONFIG_CRASH_DUMP) += crash_dump.o obj-$(CONFIG_VMCORE_INFO) += vmcore_info.o obj-$(CONFIG_ARM_SDE_INTERFACE) += sdei.o obj-$(CONFIG_ARM64_PTR_AUTH) += pointer_auth.o +obj-$(CONFIG_ARM64_MPAM) += mpam.o obj-$(CONFIG_ARM64_MTE) += mte.o obj-y += vdso-wrap.o obj-$(CONFIG_COMPAT_VDSO) += vdso32-wrap.o diff --git a/arch/arm64/kernel/mpam.c b/arch/arm64/kernel/mpam.c new file mode 100644 index 000000000000..9866d2ca0faa --- /dev/null +++ b/arch/arm64/kernel/mpam.c @@ -0,0 +1,13 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (C) 2025 Arm Ltd. */ + +#include <asm/mpam.h> + +#include <linux/jump_label.h> +#include <linux/percpu.h> + +DEFINE_STATIC_KEY_FALSE(mpam_enabled); +DEFINE_PER_CPU(u64, arm64_mpam_default); +DEFINE_PER_CPU(u64, arm64_mpam_current); + +u64 arm64_mpam_global_default; diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index 489554931231..47698955fa1e 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -51,6 +51,7 @@ #include <asm/fpsimd.h> #include <asm/gcs.h> #include <asm/mmu_context.h> +#include <asm/mpam.h> #include <asm/mte.h> #include <asm/processor.h> #include <asm/pointer_auth.h> @@ -738,6 +739,12 @@ struct task_struct *__switch_to(struct task_struct *prev, if (prev->thread.sctlr_user != next->thread.sctlr_user) update_sctlr_el1(next->thread.sctlr_user); + /* + * MPAM thread switch happens after the DSB to ensure prev's accesses + * use prev's MPAM settings. + */ + mpam_thread_switch(next); + /* the actual thread switch */ last = cpu_switch_to(prev, next); diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c index ff861291bd4e..d50461d6ff3f 100644 --- a/drivers/resctrl/mpam_devices.c +++ b/drivers/resctrl/mpam_devices.c @@ -29,8 +29,6 @@ #include "mpam_internal.h" -DEFINE_STATIC_KEY_FALSE(mpam_enabled); /* This moves to arch code */ - /* * mpam_list_lock protects the SRCU lists when writing. Once the * mpam_enabled key is enabled these lists are read-only, diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h index 7af762c98efc..a13fb9880ced 100644 --- a/drivers/resctrl/mpam_internal.h +++ b/drivers/resctrl/mpam_internal.h @@ -16,12 +16,12 @@ #include <linux/srcu.h> #include <linux/types.h> +#include <asm/mpam.h> + #define MPAM_MSC_MAX_NUM_RIS 16 struct platform_device; -DECLARE_STATIC_KEY_FALSE(mpam_enabled); - #ifdef CONFIG_MPAM_KUNIT_TEST #define PACKED_FOR_KUNIT __packed #else |