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>

diff --git a/hw/arm/boot.c b/hw/arm/boot.c
index c2b89b3bb9b6b92b0293d859712e68bf0a32bc0b..fc4e021a38a6bc1e5e2aa5b5876c999d9e536e26 100644 (file)
--- 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;
                 }
             }