From f787dd15fde7eb3f9c0f0352151a2f00a3a8f4e5 Mon Sep 17 00:00:00 2001
From: Richard Henderson <richard.henderson@linaro.org>
Date: Fri, 17 Aug 2018 14:02:45 -0400
Subject: [PATCH] target/arm: Adjust FPCR_MASK for FZ16

When support for FZ16 was added, we failed to include the bit
within FPCR_MASK, which means that it could never be set.
Continue to zero FZ16 when ARMv8.2-FP16 is not enabled.

Fixes: d81ce0ef2c4

Backports commit 0b62159be33d45d00dfa34a317c6d3da30ffb480 from qemu
---
 qemu/target/arm/cpu.h    | 2 +-
 qemu/target/arm/helper.c | 5 +++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/qemu/target/arm/cpu.h b/qemu/target/arm/cpu.h
index bcaf999f..463fbae6 100644
--- a/qemu/target/arm/cpu.h
+++ b/qemu/target/arm/cpu.h
@@ -1209,7 +1209,7 @@ void vfp_set_fpscr(CPUARMState *env, uint32_t val);
  * we store the underlying state in fpscr and just mask on read/write.
  */
 #define FPSR_MASK 0xf800009f
-#define FPCR_MASK 0x07f79f00
+#define FPCR_MASK 0x07ff9f00
 
 #define FPCR_FZ16   (1 << 19)   /* ARMv8.2+, FP16 flush-to-zero */
 #define FPCR_FZ     (1 << 24)   /* Flush-to-zero enable bit */
diff --git a/qemu/target/arm/helper.c b/qemu/target/arm/helper.c
index ae13fb44..c08a205c 100644
--- a/qemu/target/arm/helper.c
+++ b/qemu/target/arm/helper.c
@@ -10591,6 +10591,11 @@ void HELPER(vfp_set_fpscr)(CPUARMState *env, uint32_t val)
     int i;
     uint32_t changed;
 
+    /* When ARMv8.2-FP16 is not supported, FZ16 is RES0.  */
+    if (!arm_feature(env, ARM_FEATURE_V8_FP16)) {
+        val &= ~FPCR_FZ16;
+    }
+
     changed = env->vfp.xregs[ARM_VFP_FPSCR];
     env->vfp.xregs[ARM_VFP_FPSCR] = (val & 0xffc8ffff);
     env->vfp.vec_len = (val >> 16) & 7;