hulk inclusion category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/IDD55N -------------------------------- Currently, the MPAM implementation on Linux only applies isolation control to tasks' user-space, while resource allocation for execution in kernel mode is according to the root group's (Partid=0) policy. With MPAM adding L2 cache support, and given small L2 capacity, frequently switching partition policies between kernel and user space would cause L2 thrashing and degrade performance. Moreover, to support MPAM isolation for kernel-space processes, kernel space should adopt the same partition policy as user space. To ensure the Partid state is updated promptly after the CPU exits from low power mode, add wmb() barrier in the CPU_PM_EXIT flow to guarantee that. Signed-off-by: Zeng Heng <zengheng4@huawei.com> --- arch/arm64/include/asm/mpam.h | 1 + arch/arm64/kernel/cpufeature.c | 2 +- arch/arm64/kernel/mpam.c | 4 ++-- 3 files changed, 4 insertions(+), 3 deletions(-) diff --git a/arch/arm64/include/asm/mpam.h b/arch/arm64/include/asm/mpam.h index 8caac70e22ed..db4d559e8936 100644 --- a/arch/arm64/include/asm/mpam.h +++ b/arch/arm64/include/asm/mpam.h @@ -161,6 +161,7 @@ static inline void mpam_thread_switch(struct task_struct *tsk) return; /* Synchronising this write is left until the ERET to EL0 */ + write_sysreg_s(regval, SYS_MPAM1_EL1); write_sysreg_s(regval, SYS_MPAM0_EL1); WRITE_ONCE(per_cpu(arm64_mpam_current, cpu), regval); } diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 414b9d28ecd1..4cc8691dc7d8 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -2425,7 +2425,7 @@ cpu_enable_mpam(const struct arm64_cpu_capabilities *entry) * where latency sensitive tasks have to wait for a task that has * been throttled to release the lock. */ - write_sysreg_s(0, SYS_MPAM1_EL1); + write_sysreg_s(regval, SYS_MPAM1_EL1); write_sysreg_s(regval, SYS_MPAM0_EL1); } diff --git a/arch/arm64/kernel/mpam.c b/arch/arm64/kernel/mpam.c index 3f070cbab420..008c44c96a75 100644 --- a/arch/arm64/kernel/mpam.c +++ b/arch/arm64/kernel/mpam.c @@ -40,9 +40,9 @@ static int mpam_pm_notifier(struct notifier_block *self, * value has changed under our feet. */ regval = READ_ONCE(per_cpu(arm64_mpam_current, cpu)); - write_sysreg_s(0, SYS_MPAM1_EL1); + write_sysreg_s(regval, SYS_MPAM1_EL1); write_sysreg_s(regval, SYS_MPAM0_EL1); - + wmb(); return NOTIFY_OK; default: return NOTIFY_DONE; -- 2.25.1