linux-kernel - [PATCH stable 4.9] arm64: kpti: Whitelist Cortex-A CPUs that don't implement the CSV3 field

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Date:   Fri, 24 Jan 2020 12:08:20 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     will@...nel.org, gregkh@...uxfoundation.org,
        stable@...r.kernel.org, sashal@...nel.org,
        Will Deacon <will.deacon@....com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH stable 4.9] arm64: kpti: Whitelist Cortex-A CPUs that don't 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>
[florian: adjust whilelist location and table to stable-4.9.y]
Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
---
 arch/arm64/kernel/cpufeature.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 9a8e45dc36bd..8cf001baee21 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -789,6 +789,11 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
 	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;
 	}
 
-- 
2.17.1