meta-arm/meta-arm-bsp/recipes-kernel/linux/linux-yocto-5.19/n1sdp/0005-arm64-kpti-Whitelist-early-Arm-Neoverse-N1-revisions.patch

From 748cb5125b381330563b5339a4573827b015b0e9 Mon Sep 17 00:00:00 2001
From: Andre Przywara <andre.przywara@arm.com>
Date: Fri, 17 May 2019 17:39:27 +0100
Subject: [PATCH] arm64: kpti: Whitelist early Arm Neoverse N1 revisions

Early revisions (r1p0) of the Neoverse N1 core did not feature the
CSV3 field in ID_AA64PFR0_EL1 to advertise they are not affected by
the Spectre variant 3 (aka Meltdown) vulnerability.

Add this particular revision to the whitelist to avoid enabling KPTI.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>

Upstream-Status: Inappropriate
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Vishnu Banavath <vishnu.banavath@arm.com>
Signed-off-by: Adam Johnston <adam.johnston@arm.com>
---
 arch/arm64/kernel/cpufeature.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index f34c9f8b9ee0..a778cf472d64 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1589,6 +1589,7 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
 		MIDR_ALL_VERSIONS(MIDR_QCOM_KRYO_2XX_SILVER),
 		MIDR_ALL_VERSIONS(MIDR_QCOM_KRYO_3XX_SILVER),
 		MIDR_ALL_VERSIONS(MIDR_QCOM_KRYO_4XX_SILVER),
+		MIDR_REV(MIDR_NEOVERSE_N1, 1, 0),	/* missing CSV3 */
 		{ /* sentinel */ }
 	};
 	char const *str = "kpti command line option";