linux-kernel - [PATCH 4.19 78/79] arm64: kpti: Whitelist Cortex-A CPUs that dont implement the CSV3 field

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Message-Id: <20190919214814.627750263@linuxfoundation.org>
Date:   Fri, 20 Sep 2019 00:04:03 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Will Deacon <will.deacon@....com>,
        Niklas Cassel <niklas.cassel@...aro.org>
Subject: [PATCH 4.19 78/79] arm64: kpti: Whitelist Cortex-A CPUs that dont implement the CSV3 field

From: Will Deacon <will.deacon@....com>

commit 2a355ec25729053bb9a1a89b6c1d1cdd6c3b3fb1 upstream.

While the CSV3 field of the ID_AA64_PFR0 CPU ID register can be checked
to see if a CPU is susceptible to Meltdown and therefore requires kpti
to be enabled, existing CPUs do not implement this field.

We therefore whitelist all unaffected Cortex-A CPUs that do not implement
the CSV3 field.

Signed-off-by: Will Deacon <will.deacon@....com>
Cc: Niklas Cassel <niklas.cassel@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/arm64/kernel/cpufeature.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -895,6 +895,12 @@ static bool unmap_kernel_at_el0(const st
 	static const struct midr_range kpti_safe_list[] = {
 		MIDR_ALL_VERSIONS(MIDR_CAVIUM_THUNDERX2),
 		MIDR_ALL_VERSIONS(MIDR_BRCM_VULCAN),
+		MIDR_ALL_VERSIONS(MIDR_CORTEX_A35),
+		MIDR_ALL_VERSIONS(MIDR_CORTEX_A53),
+		MIDR_ALL_VERSIONS(MIDR_CORTEX_A55),
+		MIDR_ALL_VERSIONS(MIDR_CORTEX_A57),
+		MIDR_ALL_VERSIONS(MIDR_CORTEX_A72),
+		MIDR_ALL_VERSIONS(MIDR_CORTEX_A73),
 		{ /* sentinel */ }
 	};
 	char const *str = "command line option";