From 220816989c1e3d490d293b8d7ac85dbc41a4c321 Mon Sep 17 00:00:00 2001
From: Peter Maydell <peter.maydell@linaro.org>
Date: Fri, 20 Sep 2019 18:40:39 +0100
Subject: [PATCH] hw/arm/boot.c: Set NSACR.{CP11,CP10} for NS kernel boots

If we're booting a Linux kernel directly into Non-Secure
state on a CPU which has Secure state, then make sure we
set the NSACR CP11 and CP10 bits, so that Non-Secure is allowed
to access the FPU. Otherwise an AArch32 kernel will UNDEF as
soon as it tries to use the FPU.

It used to not matter that we didn't do this until commit
fc1120a7f5f2d4b6, where we implemented actually honouring
these NSACR bits.

The problem only exists for CPUs where EL3 is AArch32; the
equivalent AArch64 trap bits are in CPTR_EL3 and are "0 to
not trap, 1 to trap", so the reset value of the register
permits NS access, unlike NSACR.

Fixes: fc1120a7f5
Fixes: https://bugs.launchpad.net/qemu/+bug/1844597
Cc: qemu-stable@nongnu.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20190920174039.3916-1-peter.maydell@linaro.org
(cherry picked from commit ece628fcf69cbbd4b3efb6fbd203af07609467a2)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
---
 hw/arm/boot.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/hw/arm/boot.c b/hw/arm/boot.c
index c2b89b3bb9..fc4e021a38 100644
--- a/hw/arm/boot.c
+++ b/hw/arm/boot.c
@@ -754,6 +754,8 @@ static void do_cpu_reset(void *opaque)
                     (cs != first_cpu || !info->secure_board_setup)) {
                     /* Linux expects non-secure state */
                     env->cp15.scr_el3 |= SCR_NS;
+                    /* Set NSACR.{CP11,CP10} so NS can access the FPU */
+                    env->cp15.nsacr |= 3 << 10;
                 }
             }

--
2.23.0