target-arm: A64: Correctly fault FP/Neon if CPACR.FPEN set

For the A64 instruction set, the only FP/Neon disable trap
is the CPACR FPEN bits, which may indicate "enabled", "disabled"
or "disabled for EL0". Add a bit to the AArch64 tb flags indicating
whether FP/Neon access is currently enabled and make the decoder
emit code to raise exceptions on use of FP/Neon insns if it is not.

We use a new flag in DisasContext rather than borrowing the
existing vfp_enabled flag because the A32/T32 decoder is going
to need both.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Acked-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
---
I'm aware this is a rather hard to review patch; sorry.
I have done an exhaustive check that we have fp access checks
in all code paths with the aid of the assertions added in the
next patch plus the code-coverage hack patch I posted to the
list earlier.

This patch is correct as of
09e037354 target-arm: A64: Add saturating accumulate ops (USQADD/SUQADD)
which was the last of the Neon insns to be added, so assuming
no refactoring of the code it should be fine.

1 files changed, 7 insertions, 0 deletions

diff --git a/target-arm/cpu.c b/target-arm/cpu.c
index 0b1ad10..d62b792 100644
--- a/target-arm/cpu.c
+++ b/target-arm/cpu.c
@@ -100,9 +100,16 @@ static void arm_cpu_reset(CPUState *s)
         env->pstate = PSTATE_MODE_EL0t;
         /* Userspace expects access to CTL_EL0 and the cache ops */
         env->cp15.c1_sys |= SCTLR_UCT | SCTLR_UCI;
+        /* and to the FP/Neon instructions */
+        env->cp15.c1_coproc = deposit64(env->cp15.c1_coproc, 20, 2, 3);
 #else
         env->pstate = PSTATE_MODE_EL1h;
 #endif
+    } else {
+#if defined(CONFIG_USER_ONLY)
+        /* Userspace expects access to cp10 and cp11 for FP/Neon */
+        env->cp15.c1_coproc = deposit64(env->cp15.c1_coproc, 20, 4, 0xf);
+#endif
     }
 
 #if defined(CONFIG_USER_ONLY)