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Date: Fri, 12 Apr 2019 15:39:29 -0500
From: Josh Poimboeuf <jpoimboe@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
"H . Peter Anvin" <hpa@...or.com>,
Andy Lutomirski <luto@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Jiri Kosina <jikos@...nel.org>,
Waiman Long <longman@...hat.com>,
Andrea Arcangeli <aarcange@...hat.com>,
Jon Masters <jcm@...hat.com>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Michael Ellerman <mpe@...erman.id.au>,
linuxppc-dev@...ts.ozlabs.org,
Martin Schwidefsky <schwidefsky@...ibm.com>,
Heiko Carstens <heiko.carstens@...ibm.com>,
linux-s390@...r.kernel.org,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
linux-arm-kernel@...ts.infradead.org, linux-arch@...r.kernel.org,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Tyler Hicks <tyhicks@...onical.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Randy Dunlap <rdunlap@...radead.org>,
Steven Price <steven.price@....com>,
Phil Auld <pauld@...hat.com>
Subject: [PATCH v2 2/5] x86/speculation: Support 'mitigations=' cmdline option
Configure x86 runtime CPU speculation bug mitigations in accordance with
the 'mitigations=' cmdline option. This affects Meltdown, Spectre v2,
Speculative Store Bypass, and L1TF.
The default behavior is unchanged.
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
Documentation/admin-guide/kernel-parameters.txt | 16 +++++++++++-----
arch/x86/kernel/cpu/bugs.c | 11 +++++++++--
arch/x86/mm/pti.c | 4 +++-
3 files changed, 23 insertions(+), 8 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 3ea92e075c64..3e33bd03441a 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2545,15 +2545,20 @@
http://repo.or.cz/w/linux-2.6/mini2440.git
mitigations=
- 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.
+ [X86] 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.
off
Disable all optional CPU mitigations. This
improves system performance, but it may also
expose users to several CPU vulnerabilities.
+ Equivalent to: nopti [X86]
+ nospectre_v2 [X86]
+ spectre_v2_user=off [X86]
+ spec_store_bypass_disable=off [X86]
+ l1tf=off [X86]
auto (default)
Mitigate all CPU vulnerabilities, but leave SMT
@@ -2561,12 +2566,13 @@
users who don't want to be surprised by SMT
getting disabled across kernel upgrades, or who
have other ways of avoiding SMT-based attacks.
- This is the default behavior.
+ Equivalent to: (default behavior)
auto,nosmt
Mitigate all CPU vulnerabilities, disabling SMT
if needed. This is for users who always want to
be fully mitigated, even if it means losing SMT.
+ Equivalent to: l1tf=flush,nosmt [X86]
mminit_loglevel=
[KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 2da82eff0eb4..8043a21f36be 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -440,7 +440,8 @@ static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
char arg[20];
int ret, i;
- if (cmdline_find_option_bool(boot_command_line, "nospectre_v2"))
+ if (cmdline_find_option_bool(boot_command_line, "nospectre_v2") ||
+ cpu_mitigations_off())
return SPECTRE_V2_CMD_NONE;
ret = cmdline_find_option(boot_command_line, "spectre_v2", arg, sizeof(arg));
@@ -672,7 +673,8 @@ static enum ssb_mitigation_cmd __init ssb_parse_cmdline(void)
char arg[20];
int ret, i;
- if (cmdline_find_option_bool(boot_command_line, "nospec_store_bypass_disable")) {
+ if (cmdline_find_option_bool(boot_command_line, "nospec_store_bypass_disable") ||
+ cpu_mitigations_off()) {
return SPEC_STORE_BYPASS_CMD_NONE;
} else {
ret = cmdline_find_option(boot_command_line, "spec_store_bypass_disable",
@@ -1008,6 +1010,11 @@ static void __init l1tf_select_mitigation(void)
if (!boot_cpu_has_bug(X86_BUG_L1TF))
return;
+ if (cpu_mitigations_off())
+ l1tf_mitigation = L1TF_MITIGATION_OFF;
+ else if (cpu_mitigations_auto_nosmt())
+ l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOSMT;
+
override_cache_bits(&boot_cpu_data);
switch (l1tf_mitigation) {
diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
index 5d27172c683f..9c2463bc158f 100644
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -35,6 +35,7 @@
#include <linux/spinlock.h>
#include <linux/mm.h>
#include <linux/uaccess.h>
+#include <linux/cpu.h>
#include <asm/cpufeature.h>
#include <asm/hypervisor.h>
@@ -115,7 +116,8 @@ void __init pti_check_boottime_disable(void)
}
}
- if (cmdline_find_option_bool(boot_command_line, "nopti")) {
+ if (cmdline_find_option_bool(boot_command_line, "nopti") ||
+ cpu_mitigations_off()) {
pti_mode = PTI_FORCE_OFF;
pti_print_if_insecure("disabled on command line.");
return;
--
2.17.2
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