Patch "arm64: Provide a command line to disable spectre_v2 mitigation" has been added to the 4.19-stable tree

[<gregkh@linuxfoundation.org>]

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

    arm64: Provide a command line to disable spectre_v2 mitigation

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:
     arm64-provide-a-command-line-to-disable-spectre_v2-mitigation.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 <stable@vger.kernel.org> know about it.


From foo@baz Wed 09 Oct 2019 10:02:11 AM CEST
From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Date: Tue,  8 Oct 2019 17:39:24 +0200
Subject: arm64: Provide a command line to disable spectre_v2 mitigation
To: linux-arm-kernel@lists.infradead.org
Cc: stable@vger.kernel.org, Jeremy Linton <jeremy.linton@arm.com>, Suzuki K Poulose <suzuki.poulose@arm.com>, Andre Przywara <andre.przywara@arm.com>, Catalin Marinas <catalin.marinas@arm.com>, Stefan Wahren <stefan.wahren@i2se.com>, Jonathan Corbet <corbet@lwn.net>, linux-doc@vger.kernel.org, Will Deacon <will.deacon@arm.com>, Ard Biesheuvel <ard.biesheuvel@linaro.org>
Message-ID: <20191008153930.15386-11-ard.biesheuvel@linaro.org>

From: Jeremy Linton <jeremy.linton@arm.com>

[ Upstream commit e5ce5e7267ddcbe13ab9ead2542524e1b7993e5a ]

There are various reasons, such as benchmarking, to disable spectrev2
mitigation on a machine. Provide a command-line option to do so.

Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 Documentation/admin-guide/kernel-parameters.txt |    8 ++++----
 arch/arm64/kernel/cpu_errata.c                  |   13 +++++++++++++
 2 files changed, 17 insertions(+), 4 deletions(-)

--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2866,10 +2866,10 @@
 			(bounds 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
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -189,6 +189,14 @@ static void qcom_link_stack_sanitization
 		     : "=&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)
 {
@@ -200,6 +208,11 @@ enable_smccc_arch_workaround_1(const str
 	if (!entry->matches(entry, SCOPE_LOCAL_CPU))
 		return;
 
+	if (__nospectre_v2) {
+		pr_info_once("spectrev2 mitigation disabled by command line option\n");
+		return;
+	}
+
 	if (psci_ops.smccc_version == SMCCC_VERSION_1_0)
 		return;
 


Patches currently in stable-queue which might be from ard.biesheuvel@linaro.org are

queue-4.19/arm64-add-sysfs-vulnerability-show-for-meltdown.patch
queue-4.19/arm64-force-ssbs-on-context-switch.patch
queue-4.19/arm64-enable-generic-cpu-vulnerabilites-support.patch
queue-4.19/arm64-provide-a-command-line-to-disable-spectre_v2-mitigation.patch
queue-4.19/arm64-always-enable-spectre-v2-vulnerability-detection.patch
queue-4.19/arm64-docs-document-ssbs-hwcap.patch
queue-4.19/arm64-add-sysfs-vulnerability-show-for-spectre-v1.patch
queue-4.19/arm64-add-sysfs-vulnerability-show-for-speculative-store-bypass.patch
queue-4.19/kvm-arm64-set-sctlr_el2.dssbs-if-ssbd-is-forcefully-disabled-and-vhe.patch
queue-4.19/arm64-always-enable-ssb-vulnerability-detection.patch
queue-4.19/arm64-advertise-mitigation-of-spectre-v2-or-lack-thereof.patch
queue-4.19/arm64-ssbs-don-t-treat-cpus-with-ssbs-as-unaffected-by-ssb.patch
queue-4.19/crypto-skcipher-unmap-pages-after-an-external-error.patch
queue-4.19/arm64-cpufeature-detect-ssbs-and-advertise-to-userspace.patch
queue-4.19/arm64-ssbd-add-support-for-pstate.ssbs-rather-than-trapping-to-el3.patch
queue-4.19/arm64-fix-ssbs-sanitization.patch
queue-4.19/arm64-add-sysfs-vulnerability-show-for-spectre-v2.patch

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