lkml.org 
[lkml]   [2019]   [Jan]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v4 02/12] arm64: Provide a command line to disable spectre_v2 mitigation
Date
There are various reasons, including bencmarking, to disable spectrev2
mitigation on a machine. Provide a command-line to do so.

Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
---
Documentation/admin-guide/kernel-parameters.txt | 8 ++++----
arch/arm64/kernel/cpu_errata.c | 11 +++++++++++
2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 9475f02c79da..2ae77979488e 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2849,10 +2849,10 @@
check bypass). With this option data leaks are possible
in the system.

- nospectre_v2 [X86,PPC_FSL_BOOK3E] Disable all mitigations for the Spectre variant 2
- (indirect branch prediction) vulnerability. System may
- allow data leaks with this option, which is equivalent
- to spectre_v2=off.
+ nospectre_v2 [X86,PPC_FSL_BOOK3E,ARM64] Disable all mitigations for
+ the Spectre variant 2 (indirect branch prediction)
+ vulnerability. System may allow data leaks with this
+ option.

nospec_store_bypass_disable
[HW] Disable all mitigations for the Speculative Store Bypass vulnerability
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 9950bb0cbd52..9a7b5fca51a0 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -220,6 +220,14 @@ static void qcom_link_stack_sanitization(void)
: "=&r" (tmp));
}

+static bool __nospectre_v2;
+static int __init parse_nospectre_v2(char *str)
+{
+ __nospectre_v2 = true;
+ return 0;
+}
+early_param("nospectre_v2", parse_nospectre_v2);
+
static void
enable_smccc_arch_workaround_1(const struct arm64_cpu_capabilities *entry)
{
@@ -231,6 +239,9 @@ enable_smccc_arch_workaround_1(const struct arm64_cpu_capabilities *entry)
if (!entry->matches(entry, SCOPE_LOCAL_CPU))
return;

+ if (__nospectre_v2)
+ return;
+
if (psci_ops.smccc_version == SMCCC_VERSION_1_0)
return;

--
2.17.2
\
 
 \ /
  Last update: 2019-01-25 19:08    [W:0.309 / U:2.040 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site