From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: ACJfBot+9oDO3qazPWRNOnyV8le3EUf61bgQ+P70g6U2oL00CtjjyOfMBN7quis6y93EjB6+mSDp ARC-Seal: i=1; a=rsa-sha256; t=1516269151; cv=none; d=google.com; s=arc-20160816; b=wtM/l/P515D2CzXsr0uDLd7cji8PMzSyk8reHAGWrrjaXHGdwcBWG3svrvWJ74BOaR TfUvuCa5YcZXvCrGq3szUPVb5s82ogDOS52+7j8bfTaAhMpRDUYVH7wIUB70wzZI41cv LxsOOjunlg/sLLhJqzwxHmn2pxRLENzH717SgxanKYR10oZdixpmcWgX6Iq7dMmxctef j/ugevBVf1O9/QCOkPJhPpgVdm3ytalytE34dgi9yqQXP8L+JDjwQwS4bzYTgxPUcAqB Igx38GzijNmL3gtnH6hRhbOu9uwXhm10qi6iW2LnKdmjZP6OK4aBXkt4H1DpG49HnKFR V8kw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:mime-version:organization:references :in-reply-to:message-id:subject:cc:to:from:date :arc-authentication-results; bh=IwRI5/bP2ZbtREm1rl+fgJFBrIgDw4lzrNzRfLLu/1o=; b=XYX/HZm0Ealqj58NiOGN1pq7+RX4Fyhau7lnG05iYRzCvU5L3h9gTnoHPMxpYIG6ZD lq99QHpzOuqLC1kvdTsDI+qFAB/iqIL7fkfecrOAdbnGwOZiEyRBJk2adPeUtuVaJVM2 OngUYmzlWDk55mc76XHLQ1v1uFnQqMSbUrL5oUXtFkshBkYNcQhid77DkiLCGqngfXzB 9ZMILkwechYKq1oZRZe1b8vmqReWfzaElNKr4EObwDDSEw7+7TWGwNYDxESzYhCAKrFH LmFY+LCnMqwCeEU2UtkrXG87FQv2YY451lSGX84uIXjQHsP+ZpjomhANYgr2sod1GdnI yIww== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of cohuck@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=cohuck@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Authentication-Results: mx.google.com; spf=pass (google.com: domain of cohuck@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=cohuck@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Date: Thu, 18 Jan 2018 10:52:23 +0100 From: Cornelia Huck To: Martin Schwidefsky 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 Subject: Re: [PATCH 3/6] s390: add options to change branch prediction behaviour for the kernel Message-ID: <20180118105223.595f6c74.cohuck@redhat.com> In-Reply-To: <1516182519-10623-4-git-send-email-schwidefsky@de.ibm.com> References: <1516182519-10623-1-git-send-email-schwidefsky@de.ibm.com> <1516182519-10623-4-git-send-email-schwidefsky@de.ibm.com> Organization: Red Hat GmbH MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1589832613617096388?= X-GMAIL-MSGID: =?utf-8?q?1589923441179768819?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 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]