Messages in this thread Patch in this message | | | From | Dave Martin <> | Subject | [PATCH v2 04/35] x86/resctrl: Add helper for setting CPU default properties | Date | Fri, 26 Apr 2024 16:08:33 +0100 |
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From: James Morse <james.morse@arm.com>
rdtgroup_rmdir_ctrl() and rdtgroup_rmdir_mon() set the per-CPU pqr_state for CPUs that were part of the rmdir()'d group.
Another architecture might not have a 'pqr_state', its hardware may need the values in a different format. MPAM's equivalent of RMID values are not unique, and always need the CLOSID to be provided too.
There is only one caller that modifies a single value, (rdtgroup_rmdir_mon()). MPAM always needs both CLOSID and RMID for the hardware value as these are written to the same system register.
As rdtgroup_rmdir_mon() has the CLOSID on hand, only provide a helper to set both values. These values are read by __resctrl_sched_in(), but may be written by a different CPU without any locking, add READ/WRTE_ONCE() to avoid torn values.
Signed-off-by: James Morse <james.morse@arm.com> Signed-off-by: Dave Martin <Dave.Martin@arm.com>
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Changes in v2:
* In rdtgroup_rmdir_mon(), (re)set CPU default closid based on the parent control group, to avoid the appearance of referencing something that we're in the process of destroying (even if it doesn't make a difference because the victim mon group necessarily has the same closid as the parent control group).
Update comment to match.
No (intentional) functional change. --- arch/x86/include/asm/resctrl.h | 14 +++++++++++--- arch/x86/kernel/cpu/resctrl/rdtgroup.c | 20 ++++++++++++++------ 2 files changed, 25 insertions(+), 9 deletions(-)
diff --git a/arch/x86/include/asm/resctrl.h b/arch/x86/include/asm/resctrl.h index 12dbd2588ca7..f61382258743 100644 --- a/arch/x86/include/asm/resctrl.h +++ b/arch/x86/include/asm/resctrl.h @@ -4,8 +4,9 @@ #ifdef CONFIG_X86_CPU_RESCTRL -#include <linux/sched.h> #include <linux/jump_label.h> +#include <linux/percpu.h> +#include <linux/sched.h> /* * This value can never be a valid CLOSID, and is used when mapping a @@ -96,8 +97,8 @@ static inline void resctrl_arch_disable_mon(void) static inline void __resctrl_sched_in(struct task_struct *tsk) { struct resctrl_pqr_state *state = this_cpu_ptr(&pqr_state); - u32 closid = state->default_closid; - u32 rmid = state->default_rmid; + u32 closid = READ_ONCE(state->default_closid); + u32 rmid = READ_ONCE(state->default_rmid); u32 tmp; /* @@ -132,6 +133,13 @@ static inline unsigned int resctrl_arch_round_mon_val(unsigned int val) return val * scale; } +static inline void resctrl_arch_set_cpu_default_closid_rmid(int cpu, u32 closid, + u32 rmid) +{ + WRITE_ONCE(per_cpu(pqr_state.default_closid, cpu), closid); + WRITE_ONCE(per_cpu(pqr_state.default_rmid, cpu), rmid); +} + static inline void resctrl_arch_set_closid_rmid(struct task_struct *tsk, u32 closid, u32 rmid) { diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c index 47234562a1dd..98c051ac848d 100644 --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c @@ -3624,14 +3624,21 @@ static int rdtgroup_mkdir(struct kernfs_node *parent_kn, const char *name, static int rdtgroup_rmdir_mon(struct rdtgroup *rdtgrp, cpumask_var_t tmpmask) { struct rdtgroup *prdtgrp = rdtgrp->mon.parent; + u32 closid, rmid; int cpu; /* Give any tasks back to the parent group */ rdt_move_group_tasks(rdtgrp, prdtgrp, tmpmask); - /* Update per cpu rmid of the moved CPUs first */ + /* + * Update per cpu closid/rmid of the moved CPUs first. + * Note: the closid will not change, but the arch code still needs it. + */ + closid = prdtgrp->closid; + rmid = prdtgrp->mon.rmid; for_each_cpu(cpu, &rdtgrp->cpu_mask) - per_cpu(pqr_state.default_rmid, cpu) = prdtgrp->mon.rmid; + resctrl_arch_set_cpu_default_closid_rmid(cpu, closid, rmid); + /* * Update the MSR on moved CPUs and CPUs which have moved * task running on them. @@ -3664,6 +3671,7 @@ static int rdtgroup_ctrl_remove(struct rdtgroup *rdtgrp) static int rdtgroup_rmdir_ctrl(struct rdtgroup *rdtgrp, cpumask_var_t tmpmask) { + u32 closid, rmid; int cpu; /* Give any tasks back to the default group */ @@ -3674,10 +3682,10 @@ static int rdtgroup_rmdir_ctrl(struct rdtgroup *rdtgrp, cpumask_var_t tmpmask) &rdtgroup_default.cpu_mask, &rdtgrp->cpu_mask); /* Update per cpu closid and rmid of the moved CPUs first */ - for_each_cpu(cpu, &rdtgrp->cpu_mask) { - per_cpu(pqr_state.default_closid, cpu) = rdtgroup_default.closid; - per_cpu(pqr_state.default_rmid, cpu) = rdtgroup_default.mon.rmid; - } + closid = rdtgroup_default.closid; + rmid = rdtgroup_default.mon.rmid; + for_each_cpu(cpu, &rdtgrp->cpu_mask) + resctrl_arch_set_cpu_default_closid_rmid(cpu, closid, rmid); /* * Update the MSR on moved CPUs and CPUs which have moved -- 2.34.1
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