s390/ctl_reg: make __ctl_load a full memory barrier

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[ Upstream commit e991c24d68 ]

We have quite a lot of code that depends on the order of the
__ctl_load inline assemby and subsequent memory accesses, like
e.g. disabling lowcore protection and the writing to lowcore.

Since the __ctl_load macro does not have memory barrier semantics, nor
any other dependencies the compiler is, theoretically, free to shuffle
code around. Or in other words: storing to lowcore could happen before
lowcore protection is disabled.

In order to avoid this class of potential bugs simply add a full
memory barrier to the __ctl_load macro.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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Heiko Carstens 2016-12-28 11:33:48 +01:00 • committed by Greg Kroah-Hartman

parent 9d00195bc0

commit 0e9867b711

1 changed files with 3 additions and 1 deletions

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arch/s390/include/asm/ctl_reg.h

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