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authorJosh Poimboeuf <jpoimboe@redhat.com>2019-04-12 15:39:31 -0500
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-05-14 19:18:46 +0200
commit91788fcb21d008b1b7ac6beae20522725fa78239 (patch)
tree1d5c007fa1e6e3eec0b5969506588b84fab3a9ca
parent6c2eb44188330f72c9e7efad8a64043e08f0ccef (diff)
s390/speculation: Support 'mitigations=' cmdline option
commit 0336e04a6520bdaefdb0769d2a70084fa52e81ed 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>
-rw-r--r--Documentation/admin-guide/kernel-parameters.txt5
-rw-r--r--arch/s390/kernel/nospec-branch.c9
2 files changed, 12 insertions, 2 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 204161cee674..6fa7895885c9 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -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]
diff --git a/arch/s390/kernel/nospec-branch.c b/arch/s390/kernel/nospec-branch.c
index d5eed651b5ab..83e597688562 100644
--- a/arch/s390/kernel/nospec-branch.c
+++ b/arch/s390/kernel/nospec-branch.c
@@ -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.