The x86 kernel and the documentation use 'nopti' as the kernel command
line argument to disable kernel page table isolation, so add nopti to
the arm64 kernel for compatibility.

Signed-off-by: Mark Langsdorf <redacted>
---
  Documentation/admin-guide/kernel-parameters.txt |  6 +++---
  arch/arm64/kernel/cpufeature.c                  | 11 ++++++++++-
  2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index f2040d4..a987725 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt

@@ -3342,8 +3342,8 @@
  	pt.		[PARIDE]
  			See Documentation/blockdev/paride.txt.
  
-	pti=		[X86_64] Control Page Table Isolation of user and
-			kernel address spaces.  Disabling this feature
+	pti=		[X86_64, ARM64] Control Page Table Isolation of user
+			and kernel address spaces.  Disabling this feature
  			removes hardening, but improves performance of
  			system calls and interrupts.

@@ -3354,7 +3354,7 @@
  
  			Not specifying this option is equivalent to pti=auto.
  
-	nopti		[X86_64]
+	nopti		[X86_64, ARM64]
  			Equivalent to pti=off
  
  	pty.legacy_count=

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 9d1b06d..7c5d8712 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c

@@ -934,10 +934,19 @@ static int __init parse_kpti(char *str)
  	if (ret)
  		return ret;
  
-	__kpti_forced = enabled ? 1 : -1;
+	if (!__kpti_forced)
+		__kpti_forced = enabled ? 1 : -1;
  	return 0;
  }
  __setup("kpti=", parse_kpti);