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authorFenghua Yu <fenghua.yu@intel.com>2020-12-17 14:31:19 -0800
committerBorislav Petkov <bp@suse.de>2021-01-08 09:08:03 +0100
commita0195f314a25582b38993bf30db11c300f4f4611 (patch)
tree64fa158d93d3c5b1ccf2ff5d59a5327155a9a8fc /arch/x86
parentae28d1aae48a1258bd09a6f707ebb4231d79a761 (diff)
downloadlinux-a0195f314a25582b38993bf30db11c300f4f4611.tar.bz2
x86/resctrl: Don't move a task to the same resource group
Shakeel Butt reported in [1] that a user can request a task to be moved to a resource group even if the task is already in the group. It just wastes time to do the move operation which could be costly to send IPI to a different CPU. Add a sanity check to ensure that the move operation only happens when the task is not already in the resource group. [1] https://lore.kernel.org/lkml/CALvZod7E9zzHwenzf7objzGKsdBmVwTgEJ0nPgs0LUFU3SN5Pw@mail.gmail.com/ Fixes: e02737d5b826 ("x86/intel_rdt: Add tasks files") Reported-by: Shakeel Butt <shakeelb@google.com> Signed-off-by: Fenghua Yu <fenghua.yu@intel.com> Signed-off-by: Reinette Chatre <reinette.chatre@intel.com> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Tony Luck <tony.luck@intel.com> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/962ede65d8e95be793cb61102cca37f7bb018e66.1608243147.git.reinette.chatre@intel.com
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/kernel/cpu/resctrl/rdtgroup.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 1c6f8a60ac52..460f3e0df106 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -546,6 +546,13 @@ static void update_task_closid_rmid(struct task_struct *t)
static int __rdtgroup_move_task(struct task_struct *tsk,
struct rdtgroup *rdtgrp)
{
+ /* If the task is already in rdtgrp, no need to move the task. */
+ if ((rdtgrp->type == RDTCTRL_GROUP && tsk->closid == rdtgrp->closid &&
+ tsk->rmid == rdtgrp->mon.rmid) ||
+ (rdtgrp->type == RDTMON_GROUP && tsk->rmid == rdtgrp->mon.rmid &&
+ tsk->closid == rdtgrp->mon.parent->closid))
+ return 0;
+
/*
* Set the task's closid/rmid before the PQR_ASSOC MSR can be
* updated by them.