From: Josh Poimboeuf <jpoimboe@redhat.com>
Date: Wed, 17 Apr 2019 16:39:02 -0500
Subject: x86/speculation/mds: Add 'mitigations=' support for MDS
Git-repo: tip/tip
Git-commit: 5c14068f87d04adc73ba3f41c2a303d3c3d1fa12
Patch-mainline: Queued in a subsystem tree
References: bsc#1111331, CVE-2018-12126, CVE-2018-12127, CVE-2018-12130, CVE-2019-11091
Add MDS to the new 'mitigations=' cmdline option.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Borislav Petkov <bp@suse.de>
---
Documentation/admin-guide/kernel-parameters.txt | 2 ++
arch/x86/kernel/cpu/bugs.c | 5 +++--
2 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 9aa3543a8723..18cad2b0392a 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2556,6 +2556,7 @@
spectre_v2_user=off [X86]
spec_store_bypass_disable=off [X86,PPC]
l1tf=off [X86]
+ mds=off [X86]
auto (default)
Mitigate all CPU vulnerabilities, but leave SMT
@@ -2570,6 +2571,7 @@
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]
+ mds=full,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 3c5c3c3ba734..667c273a66d7 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -233,7 +233,7 @@ static const char * const mds_strings[] = {
static void __init mds_select_mitigation(void)
{
- if (!boot_cpu_has_bug(X86_BUG_MDS)) {
+ if (!boot_cpu_has_bug(X86_BUG_MDS) || cpu_mitigations_off()) {
mds_mitigation = MDS_MITIGATION_OFF;
return;
}
@@ -244,7 +244,8 @@ static void __init mds_select_mitigation(void)
static_branch_enable(&mds_user_clear);
- if (mds_nosmt && !boot_cpu_has(X86_BUG_MSBDS_ONLY))
+ if (!boot_cpu_has(X86_BUG_MSBDS_ONLY) &&
+ (mds_nosmt || cpu_mitigations_auto_nosmt()))
cpu_smt_disable(false);
}