From f410770293a1fbc08906474c24104a7a11943eb6 Mon Sep 17 00:00:00 2001 From: Fenghua Yu Date: Fri, 11 Nov 2016 17:02:38 -0800 Subject: [PATCH] x86/intel_rdt: Update percpu closid immeditately on CPUs affected by changee If CPUs are moved to or removed from a rdtgroup, the percpu closid storage is updated. If tasks running on an affected CPU use the percpu closid then the PQR_ASSOC MSR is only updated when the task runs through a context switch. Up to the context switch the CPUs operate on the wrong closid. This state is potentially unbound. Make the change immediately effective by invoking a smp function call on the affected CPUs which stores the new closid in the perpu storage and calls the rdt_sched_in() function which updates the MSR, if the current task uses the percpu closid. [ tglx: Made it work and massaged changelog once more ] Signed-off-by: Fenghua Yu Cc: "Ravi V Shankar" Cc: "Tony Luck" Cc: "Sai Prakhya" Cc: "Vikas Shivappa" Cc: "Ingo Molnar" Cc: "H. Peter Anvin" Link: http://lkml.kernel.org/r/1478912558-55514-3-git-send-email-fenghua.yu@intel.com Signed-off-by: Thomas Gleixner --- arch/x86/kernel/cpu/intel_rdt_rdtgroup.c | 72 ++++++++++++------------ 1 file changed, 36 insertions(+), 36 deletions(-) diff --git a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c index d6bad092f542..98edba431033 100644 --- a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c +++ b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c @@ -191,12 +191,40 @@ static int rdtgroup_cpus_show(struct kernfs_open_file *of, return ret; } +/* + * This is safe against intel_rdt_sched_in() called from __switch_to() + * because __switch_to() is executed with interrupts disabled. A local call + * from rdt_update_percpu_closid() is proteced against __switch_to() because + * preemption is disabled. + */ +static void rdt_update_cpu_closid(void *v) +{ + this_cpu_write(cpu_closid, *(int *)v); + /* + * We cannot unconditionally write the MSR because the current + * executing task might have its own closid selected. Just reuse + * the context switch code. + */ + intel_rdt_sched_in(); +} + +/* Update the per cpu closid and eventually the PGR_ASSOC MSR */ +static void rdt_update_percpu_closid(const struct cpumask *cpu_mask, int closid) +{ + int cpu = get_cpu(); + + if (cpumask_test_cpu(cpu, cpu_mask)) + rdt_update_cpu_closid(&closid); + smp_call_function_many(cpu_mask, rdt_update_cpu_closid, &closid, 1); + put_cpu(); +} + static ssize_t rdtgroup_cpus_write(struct kernfs_open_file *of, char *buf, size_t nbytes, loff_t off) { cpumask_var_t tmpmask, newmask; struct rdtgroup *rdtgrp, *r; - int ret, cpu; + int ret; if (!buf) return -EINVAL; @@ -236,8 +264,7 @@ static ssize_t rdtgroup_cpus_write(struct kernfs_open_file *of, /* Give any dropped cpus to rdtgroup_default */ cpumask_or(&rdtgroup_default.cpu_mask, &rdtgroup_default.cpu_mask, tmpmask); - for_each_cpu(cpu, tmpmask) - per_cpu(cpu_closid, cpu) = 0; + rdt_update_percpu_closid(tmpmask, rdtgroup_default.closid); } /* @@ -251,8 +278,7 @@ static ssize_t rdtgroup_cpus_write(struct kernfs_open_file *of, continue; cpumask_andnot(&r->cpu_mask, &r->cpu_mask, tmpmask); } - for_each_cpu(cpu, tmpmask) - per_cpu(cpu_closid, cpu) = rdtgrp->closid; + rdt_update_percpu_closid(tmpmask, rdtgroup_default.closid); } /* Done pushing/pulling - update this group with new mask */ @@ -780,18 +806,6 @@ static int reset_all_cbms(struct rdt_resource *r) return 0; } -/* - * MSR_IA32_PQR_ASSOC is scoped per logical CPU, so all updates - * are always in thread context. - */ -static void rdt_reset_pqr_assoc_closid(void *v) -{ - struct intel_pqr_state *state = this_cpu_ptr(&pqr_state); - - state->closid = 0; - wrmsr(MSR_IA32_PQR_ASSOC, state->rmid, 0); -} - /* * Forcibly remove all of subdirectories under root. */ @@ -799,7 +813,6 @@ static void rmdir_all_sub(void) { struct rdtgroup *rdtgrp, *tmp; struct task_struct *p, *t; - int cpu; /* move all tasks to default resource group */ read_lock(&tasklist_lock); @@ -807,14 +820,6 @@ static void rmdir_all_sub(void) t->closid = 0; read_unlock(&tasklist_lock); - get_cpu(); - /* Reset PQR_ASSOC MSR on this cpu. */ - rdt_reset_pqr_assoc_closid(NULL); - /* Reset PQR_ASSOC MSR on the rest of cpus. */ - smp_call_function_many(cpu_online_mask, rdt_reset_pqr_assoc_closid, - NULL, 1); - put_cpu(); - list_for_each_entry_safe(rdtgrp, tmp, &rdt_all_groups, rdtgroup_list) { /* Remove each rdtgroup other than root */ if (rdtgrp == &rdtgroup_default) @@ -828,15 +833,13 @@ static void rmdir_all_sub(void) cpumask_or(&rdtgroup_default.cpu_mask, &rdtgroup_default.cpu_mask, &rdtgrp->cpu_mask); + rdt_update_percpu_closid(&rdtgrp->cpu_mask, + rdtgroup_default.closid); + kernfs_remove(rdtgrp->kn); list_del(&rdtgrp->rdtgroup_list); kfree(rdtgrp); } - - /* Reset all per cpu closids to the default value */ - for_each_cpu(cpu, &rdtgroup_default.cpu_mask) - per_cpu(cpu_closid, cpu) = 0; - kernfs_remove(kn_info); } @@ -943,7 +946,6 @@ static int rdtgroup_rmdir(struct kernfs_node *kn) { struct task_struct *p, *t; struct rdtgroup *rdtgrp; - int cpu, ret = 0; rdtgrp = rdtgroup_kn_lock_live(kn); if (!rdtgrp) { @@ -962,8 +964,7 @@ static int rdtgroup_rmdir(struct kernfs_node *kn) /* Give any CPUs back to the default group */ cpumask_or(&rdtgroup_default.cpu_mask, &rdtgroup_default.cpu_mask, &rdtgrp->cpu_mask); - for_each_cpu(cpu, &rdtgrp->cpu_mask) - per_cpu(cpu_closid, cpu) = 0; + rdt_update_percpu_closid(&rdtgrp->cpu_mask, rdtgroup_default.closid); rdtgrp->flags = RDT_DELETED; closid_free(rdtgrp->closid); @@ -977,8 +978,7 @@ static int rdtgroup_rmdir(struct kernfs_node *kn) kernfs_remove(rdtgrp->kn); rdtgroup_kn_unlock(kn); - - return ret; + return 0; } static struct kernfs_syscall_ops rdtgroup_kf_syscall_ops = { -- 2.39.5