linux-kernel - [PATCH 1/6] arm64: kpti: move check for non-vulnerable CPUs to a function

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Date:   Tue,  7 Aug 2018 20:14:14 +0200
From:   Mian Yousaf Kaukab <ykaukab@...e.de>
To:     will.deacon@....com, marc.zyngier@....com
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        robert.richter@...ium.com, cwu@...erecomputing.com,
        Mian Yousaf Kaukab <ykaukab@...e.de>
Subject: [PATCH 1/6] arm64: kpti: move check for non-vulnerable CPUs to a function

Prepare to call it in generic cpu vulnerabilities support.

Signed-off-by: Mian Yousaf Kaukab <ykaukab@...e.de>
---
 arch/arm64/include/asm/cpufeature.h | 16 ++++++++++++++++
 arch/arm64/kernel/cpufeature.c      |  9 +--------
 2 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 1717ba1db35d..0b0b5b3e36ba 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -530,6 +530,22 @@ void arm64_set_ssbd_mitigation(bool state);
 static inline void arm64_set_ssbd_mitigation(bool state) {}
 #endif
 
+static inline bool is_cpu_meltdown_safe(void)
+{
+	/* List of CPUs that are not vulnerable and don't need KPTI */
+	static const struct midr_range kpti_safe_list[] = {
+		MIDR_ALL_VERSIONS(MIDR_CAVIUM_THUNDERX2),
+		MIDR_ALL_VERSIONS(MIDR_BRCM_VULCAN),
+		{ /* sentinel */ }
+	};
+
+	/* Don't force KPTI for CPUs that are not vulnerable */
+	if (is_midr_in_range_list(read_cpuid_id(), kpti_safe_list))
+		return true;
+
+	return false;
+}
+
 #endif /* __ASSEMBLY__ */
 
 #endif
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index e238b7932096..6a94f8bce35a 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -865,12 +865,6 @@ static int __kpti_forced; /* 0: not forced, >0: forced on, <0: forced off */
 static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
 				int scope)
 {
-	/* List of CPUs that are not vulnerable and don't need KPTI */
-	static const struct midr_range kpti_safe_list[] = {
-		MIDR_ALL_VERSIONS(MIDR_CAVIUM_THUNDERX2),
-		MIDR_ALL_VERSIONS(MIDR_BRCM_VULCAN),
-		{ /* sentinel */ }
-	};
 	char const *str = "command line option";
 
 	/*
@@ -894,8 +888,7 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
 	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE))
 		return true;
 
-	/* Don't force KPTI for CPUs that are not vulnerable */
-	if (is_midr_in_range_list(read_cpuid_id(), kpti_safe_list))
+	if (is_cpu_meltdown_safe())
 		return false;
 
 	/* Defer to CPU feature registers */
-- 
2.11.0