Subject: [PATCH v2 07/11] arm64: Convert CONFIG_ARM64_GCS to FTR_CONFIG()

From: Marc Zyngier <[email-masked]>
Date: Mon, 2 Mar 2026 11:56:48 +0000

While CONFIG_ARM64_GCS=n prevents userspace from using GCS,
the sanitised ID registers still advertise the feature.

Make it clear that nothing in the kernel should rely on this by
marking the feature as hidden for all when CONFIG_ARM64_GCS=n.

This is functionnaly equivalent to using arm64.nogcs on the kernel
command-line.

Signed-off-by: Marc Zyngier <[email-masked]>
---
 arch/arm64/kernel/cpufeature.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index cf1e53aa8e475..ab0a7d72608d4 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -308,7 +308,7 @@ static const struct arm64_ftr_bits ftr_id_aa64pfr0[] = {
 
 static const struct arm64_ftr_bits ftr_id_aa64pfr1[] = {
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR1_EL1_DF2_SHIFT, 4, 0),
-	ARM64_FTR_BITS(FTR_VISIBLE_IF_IS_ENABLED(CONFIG_ARM64_GCS),
+	ARM64_FTR_BITS(FTR_CONFIG(CONFIG_ARM64_GCS, VISIBLE, ALL_HIDDEN),
 		       FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR1_EL1_GCS_SHIFT, 4, 0),
 	S_ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR1_EL1_MTE_frac_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_CONFIG(CONFIG_ARM64_SME, VISIBLE, ALL_HIDDEN),
-- 
2.47.3