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 <[email protected]>
Cc: "Ravi V Shankar" <[email protected]>
Cc: "Tony Luck" <[email protected]>
Cc: "Marcelo Tosatti" <[email protected]>
Cc: "Sai Prakhya" <[email protected]>
Cc: "Vikas Shivappa" <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>

diff --git a/arch/x86/include/asm/intel_rdt.h b/arch/x86/include/asm/intel_rdt.h
index 6e90e87eadfe7b727e29ff2289d418c71c5f9e06..95ce5c85b0096bf81d8d5837fedfb4f7401708b9 100644 (file)
--- 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 fb8e03e2b70dc962fa3a43827eff0efd71d5fc5b..1afd3f393501c7b164d5f8cd65aa0fb39789e8ba 100644 (file)
--- 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);
 }