[PATCH] arm64: Avoid enabling KPTI unnecessarily

[Ard Biesheuvel]

From: Ard Biesheuvel <ardb at kernel.org>

Commit 42c5a3b04bf6 refactored the KPTI init code in a way that results
in the use of non-global kernel mappings even on systems that have no
need for it, and even when KPTI has been disabled explicitly via the
command line.

Ensure that this only happens when we have decided (based on the
detected CPU features) that KPTI should be enabled.

Fixes: 42c5a3b04bf6 ("arm64: Split kpti_install_ng_mappings()")
Signed-off-by: Ard Biesheuvel <ardb at kernel.org>
---
 arch/arm64/kernel/cpufeature.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 646591c67e7a..4b1762b9c37c 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -3352,7 +3352,8 @@ void __init setup_system_features(void)
 	 */
 	enable_cpu_capabilities(SCOPE_ALL & ~SCOPE_BOOT_CPU);
 
-	kpti_install_ng_mappings();
+	if (arm64_kernel_unmapped_at_el0())
+		kpti_install_ng_mappings();
 
 	sve_setup();
 	sme_setup();
-- 
2.39.2