Subject: Patch "[PATCH 24/30] x86/speculation: Support 'mitigations=' cmdline option" has been added to the 4.19-stable tree

From: <[email-masked]>
Date: Tue, 14 May 2019 19:06:14 +0200

This is a note to let you know that I've just added the patch titled

    [PATCH 24/30] x86/speculation: Support 'mitigations=' cmdline option

to the 4.19-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     0024-x86-speculation-Support-mitigations-cmdline-option.patch
and it can be found in the queue-4.19 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <[email-masked]> know about it.

>From 06fea97f2d216af0c5cb34c617301f378f4b8031 Mon Sep 17 00:00:00 2001
From: Josh Poimboeuf <[email-masked]>
Date: Fri, 12 Apr 2019 15:39:29 -0500
Subject: [PATCH 24/30] x86/speculation: Support 'mitigations=' cmdline option

commit d68be4c4d31295ff6ae34a8ddfaa4c1a8ff42812 upstream

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 <[email-masked]>
Signed-off-by: Thomas Gleixner <[email-masked]>
Tested-by: Jiri Kosina <[email-masked]> (on x86)
Reviewed-by: Jiri Kosina <[email-masked]>
Cc: Borislav Petkov <[email-masked]>
Cc: "H . Peter Anvin" <[email-masked]>
Cc: Andy Lutomirski <[email-masked]>
Cc: Peter Zijlstra <[email-masked]>
Cc: Jiri Kosina <[email-masked]>
Cc: Waiman Long <[email-masked]>
Cc: Andrea Arcangeli <[email-masked]>
Cc: Jon Masters <[email-masked]>
Cc: Benjamin Herrenschmidt <[email-masked]>
Cc: Paul Mackerras <[email-masked]>
Cc: Michael Ellerman <[email-masked]>
Cc: [email-masked]
Cc: Martin Schwidefsky <[email-masked]>
Cc: Heiko Carstens <[email-masked]>
Cc: [email-masked]
Cc: Catalin Marinas <[email-masked]>
Cc: Will Deacon <[email-masked]>
Cc: [email-masked]
Cc: [email-masked]
Cc: Greg Kroah-Hartman <[email-masked]>
Cc: Tyler Hicks <[email-masked]>
Cc: Linus Torvalds <[email-masked]>
Cc: Randy Dunlap <[email-masked]>
Cc: Steven Price <[email-masked]>
Cc: Phil Auld <[email-masked]>
Link: https://lkml.kernel.org/r/[email-masked]
Signed-off-by: Greg Kroah-Hartman <[email-masked]>
---
 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 6a1b94afb005..31c17532c219 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2503,15 +2503,20 @@
 			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
@@ -2519,12 +2524,13 @@
 				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 8d432a3d38a3..904d55cf80a2 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -494,7 +494,8 @@ 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));
@@ -756,7 +757,8 @@ 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",
@@ -1077,6 +1079,11 @@ 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 c1fc1ae6b429..4df3e5c89d57 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;
-- 
2.21.0

Patches currently in stable-queue which might be from [email-masked] are

queue-4.19/0025-powerpc-speculation-Support-mitigations-cmdline-opti.patch
queue-4.19/0022-x86-speculation-mds-Print-SMT-vulnerable-on-MSBDS-wi.patch
queue-4.19/0024-x86-speculation-Support-mitigations-cmdline-option.patch
queue-4.19/0023-cpu-speculation-Add-mitigations-cmdline-option.patch
queue-4.19/0018-x86-speculation-mds-Add-mds-full-nosmt-cmdline-optio.patch
queue-4.19/0030-x86-speculation-mds-Fix-documentation-typo.patch
queue-4.19/0027-x86-speculation-mds-Add-mitigations-support-for-MDS.patch
queue-4.19/0020-x86-speculation-mds-Add-SMT-warning-message.patch
queue-4.19/0001-Documentation-l1tf-Fix-small-spelling-typo.patch
queue-4.19/0019-x86-speculation-Move-arch_smt_update-call-to-after-m.patch
queue-4.19/0026-s390-speculation-Support-mitigations-cmdline-option.patch
queue-4.19/0021-x86-speculation-mds-Fix-comment.patch

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