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Subject[PATCH 4.9 262/271] arm64: kpti: Whitelist Cortex-A CPUs that dont implement the CSV3 field
From: Will Deacon <>

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 <>
[florian: adjust whilelist location and table to stable-4.9.y]
Signed-off-by: Florian Fainelli <>
Signed-off-by: Greg Kroah-Hartman <>

arch/arm64/kernel/cpufeature.c | 5 +++++
1 file changed, 5 insertions(+)

--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -789,6 +789,11 @@ static bool unmap_kernel_at_el0(const st
switch (read_cpuid_id() & MIDR_CPU_MODEL_MASK) {
+ case MIDR_CORTEX_A53:
+ case MIDR_CORTEX_A55:
+ case MIDR_CORTEX_A57:
+ case MIDR_CORTEX_A72:
+ case MIDR_CORTEX_A73:
return false;

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