Commit d68be4c4 authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Thomas Gleixner

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: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Tested-by: Jiri Kosina <jkosina@suse.cz> (on x86)
Reviewed-by: default avatarJiri 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/6616d0ae169308516cfdf5216bedd169f8a8291b.1555085500.git.jpoimboe@redhat.com
parent 98af8452
...@@ -2514,15 +2514,20 @@ ...@@ -2514,15 +2514,20 @@
http://repo.or.cz/w/linux-2.6/mini2440.git http://repo.or.cz/w/linux-2.6/mini2440.git
mitigations= mitigations=
Control optional mitigations for CPU vulnerabilities. [X86] Control optional mitigations for CPU
This is a set of curated, arch-independent options, each vulnerabilities. This is a set of curated,
of which is an aggregation of existing arch-specific arch-independent options, each of which is an
options. aggregation of existing arch-specific options.
off off
Disable all optional CPU mitigations. This Disable all optional CPU mitigations. This
improves system performance, but it may also improves system performance, but it may also
expose users to several CPU vulnerabilities. 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) auto (default)
Mitigate all CPU vulnerabilities, but leave SMT Mitigate all CPU vulnerabilities, but leave SMT
...@@ -2530,12 +2535,13 @@ ...@@ -2530,12 +2535,13 @@
users who don't want to be surprised by SMT users who don't want to be surprised by SMT
getting disabled across kernel upgrades, or who getting disabled across kernel upgrades, or who
have other ways of avoiding SMT-based attacks. have other ways of avoiding SMT-based attacks.
This is the default behavior. Equivalent to: (default behavior)
auto,nosmt auto,nosmt
Mitigate all CPU vulnerabilities, disabling SMT Mitigate all CPU vulnerabilities, disabling SMT
if needed. This is for users who always want to if needed. This is for users who always want to
be fully mitigated, even if it means losing SMT. be fully mitigated, even if it means losing SMT.
Equivalent to: l1tf=flush,nosmt [X86]
mminit_loglevel= mminit_loglevel=
[KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
......
...@@ -440,7 +440,8 @@ static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void) ...@@ -440,7 +440,8 @@ static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
char arg[20]; char arg[20];
int ret, i; 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; return SPECTRE_V2_CMD_NONE;
ret = cmdline_find_option(boot_command_line, "spectre_v2", arg, sizeof(arg)); 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) ...@@ -672,7 +673,8 @@ static enum ssb_mitigation_cmd __init ssb_parse_cmdline(void)
char arg[20]; char arg[20];
int ret, i; 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; return SPEC_STORE_BYPASS_CMD_NONE;
} else { } else {
ret = cmdline_find_option(boot_command_line, "spec_store_bypass_disable", ret = cmdline_find_option(boot_command_line, "spec_store_bypass_disable",
...@@ -996,6 +998,11 @@ static void __init l1tf_select_mitigation(void) ...@@ -996,6 +998,11 @@ static void __init l1tf_select_mitigation(void)
if (!boot_cpu_has_bug(X86_BUG_L1TF)) if (!boot_cpu_has_bug(X86_BUG_L1TF))
return; 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); override_cache_bits(&boot_cpu_data);
switch (l1tf_mitigation) { switch (l1tf_mitigation) {
......
...@@ -35,6 +35,7 @@ ...@@ -35,6 +35,7 @@
#include <linux/spinlock.h> #include <linux/spinlock.h>
#include <linux/mm.h> #include <linux/mm.h>
#include <linux/uaccess.h> #include <linux/uaccess.h>
#include <linux/cpu.h>
#include <asm/cpufeature.h> #include <asm/cpufeature.h>
#include <asm/hypervisor.h> #include <asm/hypervisor.h>
...@@ -115,7 +116,8 @@ void __init pti_check_boottime_disable(void) ...@@ -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_mode = PTI_FORCE_OFF;
pti_print_if_insecure("disabled on command line."); pti_print_if_insecure("disabled on command line.");
return; return;
......
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