linux-kernel - [tip:x86/cache] x86/intel_rdt: Call intel_rdt_sched

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Message-ID: <tip-74fcdae1a7fdf30de5413ccc1eca271415d01124@git.kernel.org>
Date:   Thu, 1 Dec 2016 16:18:42 -0800
From:   tip-bot for Fenghua Yu <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     vikas.shivappa@...ux.intel.com, mingo@...nel.org,
        tony.luck@...el.com, mtosatti@...hat.com,
        sai.praneeth.prakhya@...el.com, tglx@...utronix.de,
        h.peter.anvin@...el.com, ravi.v.shankar@...el.com, hpa@...or.com,
        linux-kernel@...r.kernel.org, fenghua.yu@...el.com
Subject: [tip:x86/cache] x86/intel_rdt: Call intel_rdt_sched_in() with
 preemption disabled

Commit-ID:  74fcdae1a7fdf30de5413ccc1eca271415d01124
Gitweb:     http://git.kernel.org/tip/74fcdae1a7fdf30de5413ccc1eca271415d01124
Author:     Fenghua Yu <fenghua.yu@...el.com>
AuthorDate: Thu, 1 Dec 2016 12:55:14 -0800
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Fri, 2 Dec 2016 01:13:02 +0100

x86/intel_rdt: Call intel_rdt_sched_in() with preemption disabled

intel_rdt_sched_in() must be called with preemption disabled because the
function accesses percpu variables (pqr_state and closid).

If a task moves itself via move_myself() preemption is enabled, which
violates the calling convention and can result in incorrect closid
selection when the task gets preempted or migrated.

Add the required protection and a comment about the calling convention.

Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
Cc: "Ravi V Shankar" <ravi.v.shankar@...el.com>
Cc: "Tony Luck" <tony.luck@...el.com>
Cc: "Marcelo Tosatti" <mtosatti@...hat.com>
Cc: "Sai Prakhya" <sai.praneeth.prakhya@...el.com>
Cc: "Vikas Shivappa" <vikas.shivappa@...ux.intel.com>
Cc: "H. Peter Anvin" <h.peter.anvin@...el.com>
Link: http://lkml.kernel.org/r/1480625714-54246-1-git-send-email-fenghua.yu@intel.com
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

---
 arch/x86/include/asm/intel_rdt.h         | 2 ++
 arch/x86/kernel/cpu/intel_rdt_rdtgroup.c | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/arch/x86/include/asm/intel_rdt.h b/arch/x86/include/asm/intel_rdt.h
index 6e90e87..95ce5c8 100644
--- a/arch/x86/include/asm/intel_rdt.h
+++ b/arch/x86/include/asm/intel_rdt.h
@@ -192,6 +192,8 @@ int rdtgroup_schemata_show(struct kernfs_open_file *of,
  *   resctrl file system.
  * - Caches the per cpu CLOSid values and does the MSR write only
  *   when a task with a different CLOSid is scheduled in.
+ *
+ * Must be called with preemption disabled.
  */
 static inline void intel_rdt_sched_in(void)
 {
diff --git a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
index fb8e03e..1afd3f3 100644
--- a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
+++ b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
@@ -326,8 +326,10 @@ static void move_myself(struct callback_head *head)
 		kfree(rdtgrp);
 	}
 
+	preempt_disable();
 	/* update PQR_ASSOC MSR to make resource group go into effect */
 	intel_rdt_sched_in();
+	preempt_enable();
 
 	kfree(callback);
 }