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Commit 7ae60d00 authored by Martin Schwidefsky's avatar Martin Schwidefsky Committed by Greg Kroah-Hartman
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s390: do not bypass BPENTER for interrupt system calls 



[ Upstream commit d5feec04fe578c8dbd9e2e1439afc2f0af761ed4 ]

The system call path can be interrupted before the switch back to the
standard branch prediction with BPENTER has been done. The critical
section cleanup code skips forward to .Lsysc_do_svc and bypasses the
BPENTER. In this case the kernel and all subsequent code will run with
the limited branch prediction.

Fixes: eacf67eb9b32 ("s390: run user space and KVM guests with modified branch prediction")
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 49a48a0e

arch/s390/kernel/entry.S

+2 −1
Original line number Diff line number Diff line
@@ -1316,7 +1316,8 @@ cleanup_critical: 
	srag	%r9,%r9,23

	jz	0f

	mvc	__TI_last_break(8,%r12),16(%r11)

0:	# set up saved register r11

0:	BPENTER __TI_flags(%r12),_TIF_ISOLATE_BP

	# set up saved register r11

	lg	%r15,__LC_KERNEL_STACK

	la	%r9,STACK_FRAME_OVERHEAD(%r15)

	stg	%r9,24(%r11)		# r11 pt_regs pointer