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From: Martin Schwidefsky <schwidefsky@de.ibm.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>, stable@vger.kernel.org
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Subject: [PATCH 12/19] s390: do not bypass BPENTER for interrupt system calls
Date: Fri, 27 Apr 2018 07:36:50 +0200	[thread overview]
Message-ID: <20180427053657.56944-13-schwidefsky@de.ibm.com> (raw)
In-Reply-To: <20180427053657.56944-1-schwidefsky@de.ibm.com>

[ 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: Martin Schwidefsky <schwidefsky@de.ibm.com>
---
 arch/s390/kernel/entry.S | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 8cbe75d7353d..c3e28af207cf 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -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
-- 
2.13.5

  parent reply	other threads:[~2018-04-27  5:37 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-27  5:36 [PATCH 00/19] s390 spectre mititgation for 4.9 Martin Schwidefsky
2018-04-27  5:36 ` [PATCH 01/19] s390: introduce CPU alternatives Martin Schwidefsky
2018-04-27  5:36 ` [PATCH 02/19] s390: enable CPU alternatives unconditionally Martin Schwidefsky
2018-04-27  5:36 ` [PATCH 03/19] KVM: s390: wire up bpb feature Martin Schwidefsky
2018-04-27  5:36 ` [PATCH 04/19] s390: scrub registers on kernel entry and KVM exit Martin Schwidefsky
2018-04-27  5:36 ` [PATCH 05/19] s390: add optimized array_index_mask_nospec Martin Schwidefsky
2018-04-27  5:36 ` [PATCH 06/19] s390/alternative: use a copy of the facility bit mask Martin Schwidefsky
2018-04-27  5:36 ` [PATCH 07/19] s390: add options to change branch prediction behaviour for the kernel Martin Schwidefsky
2018-04-27  5:36 ` [PATCH 08/19] s390: run user space and KVM guests with modified branch prediction Martin Schwidefsky
2018-04-27  5:36 ` [PATCH 09/19] s390: introduce execute-trampolines for branches Martin Schwidefsky
2018-04-27  5:36 ` [PATCH 10/19] KVM: s390: force bp isolation for VSIE Martin Schwidefsky
2018-04-27  5:36 ` [PATCH 11/19] s390: Replace IS_ENABLED(EXPOLINE_*) with IS_ENABLED(CONFIG_EXPOLINE_*) Martin Schwidefsky
2018-04-27  5:36 ` Martin Schwidefsky [this message]
2018-04-27  5:36 ` [PATCH 13/19] s390/entry.S: fix spurious zeroing of r0 Martin Schwidefsky
2018-04-27  5:36 ` [PATCH 14/19] s390: move nobp parameter functions to nospec-branch.c Martin Schwidefsky
2018-04-27  5:36 ` [PATCH 15/19] s390: add automatic detection of the spectre defense Martin Schwidefsky
2018-04-27  5:36 ` [PATCH 16/19] s390: report spectre mitigation via syslog Martin Schwidefsky
2018-04-27  5:36 ` [PATCH 17/19] s390: add sysfs attributes for spectre Martin Schwidefsky
2018-04-27  5:36 ` [PATCH 18/19] s390: correct nospec auto detection init order Martin Schwidefsky
2018-04-27  5:36 ` [PATCH 19/19] s390: correct module section names for expoline code revert Martin Schwidefsky
2018-04-27 10:11 ` [PATCH 00/19] s390 spectre mititgation for 4.9 Greg Kroah-Hartman
  -- strict thread matches above, loose matches on Subject: below --
2018-04-27  5:36 [PATCH 00/19] s390 spectre mititgation for 4.14 Martin Schwidefsky
2018-04-27  5:36 ` [PATCH 12/19] s390: do not bypass BPENTER for interrupt system calls Martin Schwidefsky

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