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
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committed by
Borislav Petkov
parent
ae28d1aae4
commit
a0195f314a
@ -546,6 +546,13 @@ static void update_task_closid_rmid(struct task_struct *t)
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static int __rdtgroup_move_task(struct task_struct *tsk,
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struct rdtgroup *rdtgrp)
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{
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/* If the task is already in rdtgrp, no need to move the task. */
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if ((rdtgrp->type == RDTCTRL_GROUP && tsk->closid == rdtgrp->closid &&
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tsk->rmid == rdtgrp->mon.rmid) ||
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(rdtgrp->type == RDTMON_GROUP && tsk->rmid == rdtgrp->mon.rmid &&
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tsk->closid == rdtgrp->mon.parent->closid))
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return 0;
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/*
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* Set the task's closid/rmid before the PQR_ASSOC MSR can be
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* updated by them.
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