Subject: [PATCH 1/2] arm64: Simplify early check for broken TX1 when KASLR is enabled

From: Will Deacon <[email-masked]>
Date: Wed, 15 Jan 2020 14:28:59 +0000

Now that the decision to use non-global mappings is stored in a variable,
the check to avoid enabling them for the terminally broken ThunderX1
platform can be simplified so that it is only keyed off the MIDR value.

Signed-off-by: Will Deacon <[email-masked]>
---
 arch/arm64/kernel/cpufeature.c | 15 ++++-----------
 1 file changed, 4 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 4a031111ceb5..d5242b44dc5a 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -980,9 +980,7 @@ has_useable_cnp(const struct arm64_cpu_capabilities *entry, int scope)
  */
 bool kaslr_requires_kpti(void)
 {
-	bool tx1_bug;
 	u64 ftr;
-
 	if (!IS_ENABLED(CONFIG_RANDOMIZE_BASE))
 		return false;
 
@@ -1000,18 +998,13 @@ bool kaslr_requires_kpti(void)
 	 * Systems affected by Cavium erratum 24756 are incompatible
 	 * with KPTI.
 	 */
-	if (!IS_ENABLED(CONFIG_CAVIUM_ERRATUM_27456)) {
-		tx1_bug = false;
-	} else if (!static_branch_likely(&arm64_const_caps_ready)) {
+	if (IS_ENABLED(CONFIG_CAVIUM_ERRATUM_27456)) {
 		extern const struct midr_range cavium_erratum_27456_cpus[];
 
-		tx1_bug = is_midr_in_range_list(read_cpuid_id(),
-						cavium_erratum_27456_cpus);
-	} else {
-		tx1_bug = __cpus_have_const_cap(ARM64_WORKAROUND_CAVIUM_27456);
+		if (is_midr_in_range_list(read_cpuid_id(),
+					  cavium_erratum_27456_cpus))
+			return false;
 	}
-	if (tx1_bug)
-		return false;
 
 	return kaslr_offset() > 0;
 }
-- 
2.25.0.rc1.283.g88dfdc4193-goog

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