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Commit f4107702 authored by Fenghua Yu's avatar Fenghua Yu Committed by Thomas Gleixner
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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: default avatarFenghua Yu <fenghua.yu@intel.com>
Cc: "Ravi V Shankar" <ravi.v.shankar@intel.com>
Cc: "Tony Luck" <tony.luck@intel.com>
Cc: "Sai Prakhya" <sai.praneeth.prakhya@intel.com>
Cc: "Vikas Shivappa" <vikas.shivappa@linux.intel.com>
Cc: "Ingo Molnar" <mingo@elte.hu>
Cc: "H. Peter Anvin" <h.peter.anvin@intel.com>
Link: http://lkml.kernel.org/r/1478912558-55514-3-git-send-email-fenghua.yu@intel.com


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent c7cc0cc1

arch/x86/kernel/cpu/intel_rdt_rdtgroup.c

+36 −36
Original line number Diff line number Diff line
@@ -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 = {