From c6e27f5697c28e188739ea1b4994dc8869dfb6c2 Mon Sep 17 00:00:00 2001
From: John Baldwin <jhb@FreeBSD.org>
Date: Fri, 8 Jan 2021 14:56:54 -0800
Subject: [PATCH] arm64: Clear FPU flags in the pcb in cpu_copy_thread().

New threads start off with clean FPU state instead of inheriting state
from the parent thread.

PR:		247945
Sponsored by:	Netflix
---
 sys/arm64/arm64/vm_machdep.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/sys/arm64/arm64/vm_machdep.c b/sys/arm64/arm64/vm_machdep.c
index 37fcf022452..90d628a7d6e 100644
--- a/sys/arm64/arm64/vm_machdep.c
+++ b/sys/arm64/arm64/vm_machdep.c
@@ -175,6 +175,7 @@ cpu_copy_thread(struct thread *td, struct thread *td0)
 	td->td_pcb->pcb_x[9] = (uintptr_t)td;
 	td->td_pcb->pcb_lr = (uintptr_t)fork_trampoline;
 	td->td_pcb->pcb_sp = (uintptr_t)td->td_frame;
+	td->td_pcb->pcb_fpflags &= ~(PCB_FP_STARTED | PCB_FP_KERN | PCB_FP_NOSAVE);
 	td->td_pcb->pcb_fpusaved = &td->td_pcb->pcb_fpustate;
 	td->td_pcb->pcb_vfpcpu = UINT_MAX;