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s390/speculation: Support 'mitigations=' cmdline option

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commit 0336e04a65 upstream

Configure s390 runtime CPU speculation bug mitigations in accordance
with the 'mitigations=' cmdline option.  This affects Spectre v1 and
Spectre v2.

The default behavior is unchanged.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Jiri Kosina <jkosina@suse.cz> (on x86)
Reviewed-by: Jiri Kosina <jkosina@suse.cz>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Jon Masters <jcm@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: linux-s390@vger.kernel.org
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-arch@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Tyler Hicks <tyhicks@canonical.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Steven Price <steven.price@arm.com>
Cc: Phil Auld <pauld@redhat.com>
Link: https://lkml.kernel.org/r/e4a161805458a5ec88812aac0307ae3908a030fc.1555085500.git.jpoimboe@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Josh Poimboeuf
2019-04-12 15:39:31 -05:00
committed by Greg Kroah-Hartman
parent 6c2eb44188
commit 91788fcb21
2 changed files with 12 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

5
Documentation/admin-guide/kernel-parameters.txt
View File

@@ -2389,7 +2389,7 @@
http://repo.or.cz/w/linux-2.6/mini2440.git
mitigations=
[X86,PPC] Control optional mitigations for CPU
[X86,PPC,S390] Control optional mitigations for CPU
vulnerabilities. This is a set of curated,
arch-independent options, each of which is an
aggregation of existing arch-specific options.
@@ -2400,7 +2400,8 @@
expose users to several CPU vulnerabilities.
Equivalent to: nopti [X86,PPC]
nospectre_v1 [PPC]
nospectre_v2 [X86,PPC]
nobp=0 [S390]
nospectre_v2 [X86,PPC,S390]
spectre_v2_user=off [X86]
spec_store_bypass_disable=off [X86,PPC]
l1tf=off [X86]

9
arch/s390/kernel/nospec-branch.c
View File

@@ -1,6 +1,7 @@
// SPDX-License-Identifier: GPL-2.0
#include <linux/module.h>
#include <linux/device.h>
#include <linux/cpu.h>
#include <asm/facility.h>
#include <asm/nospec-branch.h>
@@ -55,8 +56,16 @@ static int __init nospectre_v2_setup_early(char *str)
}
early_param("nospectre_v2", nospectre_v2_setup_early);
void __init nospec_auto_detect(void)
{
if (cpu_mitigations_off()) {
/*
* Disable expolines and disable nobp.
*/
if (IS_ENABLED(CC_USING_EXPOLINE))
nospec_disable = 1;
__clear_facility(82, S390_lowcore.alt_stfle_fac_list);
if (IS_ENABLED(CC_USING_EXPOLINE)) {
/*
* The kernel has been compiled with expolines.