[PATCH 4.14 014/185] arm64: kpti: Whitelist Cortex-A CPUs that dont implement the CSV3 field

[Greg Kroah-Hartman]

From: Will Deacon <will.deacon@xxxxxxx>

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@xxxxxxx>
Signed-off-by: Niklas Cassel <niklas.cassel@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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

--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -838,6 +838,11 @@ static bool unmap_kernel_at_el0(const st
 	switch (read_cpuid_id() & MIDR_CPU_MODEL_MASK) {
 	case MIDR_CAVIUM_THUNDERX2:
 	case MIDR_BRCM_VULCAN:
+	case MIDR_CORTEX_A53:
+	case MIDR_CORTEX_A55:
+	case MIDR_CORTEX_A57:
+	case MIDR_CORTEX_A72:
+	case MIDR_CORTEX_A73:
 		return false;
 	}