From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cornelia Huck Subject: Re: [PATCH 3/6] s390: add options to change branch prediction behaviour for the kernel Date: Thu, 18 Jan 2018 10:52:23 +0100 Message-ID: <20180118105223.595f6c74.cohuck@redhat.com> References: <1516182519-10623-1-git-send-email-schwidefsky@de.ibm.com> <1516182519-10623-4-git-send-email-schwidefsky@de.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org, Heiko Carstens , Paolo Bonzini , Greg Kroah-Hartman , Jon Masters , Marcus Meissner , Jiri Kosina To: Martin Schwidefsky Return-path: In-Reply-To: <1516182519-10623-4-git-send-email-schwidefsky@de.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Wed, 17 Jan 2018 10:48:36 +0100 Martin Schwidefsky wrote: > Add the PPA instruction to the system entry and exit path to switch > the kernel to a different branch prediction behaviour. The instructions > are added via CPU alternatives and can be disabled with the "nospec" > or the "nobp=0" kernel parameter. If the default behaviour selected > with CONFIG_KERNEL_NOBP is set to "n" then the "nobp=1" parameter can be > used to enable the changed kernel branch prediction. > > Acked-by: Christian Borntraeger > Signed-off-by: Martin Schwidefsky > --- > arch/s390/Kconfig | 17 +++++++++++++ > arch/s390/include/asm/processor.h | 1 + > arch/s390/kernel/alternative.c | 23 ++++++++++++++++++ > arch/s390/kernel/early.c | 2 ++ > arch/s390/kernel/entry.S | 50 ++++++++++++++++++++++++++++++++++++++- > arch/s390/kernel/ipl.c | 1 + > arch/s390/kernel/smp.c | 2 ++ > 7 files changed, 95 insertions(+), 1 deletion(-) Acked-by: Cornelia Huck [This looks sane; but as I don't have insight into the details of the new instructions, I don't feel confident enough to give a R-b]