Commit 58e106e7 authored by Balbir Singh's avatar Balbir Singh Committed by Thomas Gleixner
Browse files

sched: Add task_work callback for paranoid L1D flush 



The upcoming paranoid L1D flush infrastructure allows to conditionally
(opt-in) flush L1D in switch_mm() as a defense against potential new side
channels or for paranoia reasons. As the flush makes only sense when a task
runs on a non-SMT enabled core, because SMT siblings share L1, the
switch_mm() logic will kill a task which is flagged for L1D flush when it
is running on a SMT thread.

Add a taskwork callback so switch_mm() can queue a SIG_KILL command which
is invoked when the task tries to return to user space.

Signed-off-by: default avatarBalbir Singh <sblbir@amazon.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210108121056.21940-1-sblbir@amazon.com
parent 371b09c6

arch/Kconfig

+3 −0
Original line number Diff line number Diff line
@@ -1282,6 +1282,9 @@ config ARCH_SPLIT_ARG64 
config ARCH_HAS_ELFCORE_COMPAT

	bool



config ARCH_HAS_PARANOID_L1D_FLUSH

	bool



source "kernel/gcov/Kconfig"



source "scripts/gcc-plugins/Kconfig"

include/linux/sched.h

+10 −0
Original line number Diff line number Diff line
@@ -1400,6 +1400,16 @@ struct task_struct { 
	struct llist_head               kretprobe_instances;

#endif



#ifdef CONFIG_ARCH_HAS_PARANOID_L1D_FLUSH

	/*

	 * If L1D flush is supported on mm context switch

	 * then we use this callback head to queue kill work

	 * to kill tasks that are not running on SMT disabled

	 * cores

	 */

	struct callback_head		l1d_flush_kill;

#endif



	/*

	 * New fields for task_struct should be added above here, so that

	 * they are included in the randomized portion of task_struct.