From: Will Deacon <will@kernel.org>
Date: Wed, 15 Jan 2020 13:59:58 +0000 (+0000)
Subject: arm64: Simplify early check for broken TX1 when KASLR is enabled
X-Git-Tag: v5.6-rc1~208^2~4^4~2
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=ebac96ede61a1a46bdef12df3c1f9c20b00f2d88;p=thirdparty%2Fkernel%2Flinux.git

arm64: Simplify early check for broken TX1 when KASLR is enabled

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.

Acked-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
---

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 4a031111ceb5e..d5242b44dc5a2 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;
 }