[Qemu-stable] [PATCH 1/6] target/arm: Adjust FPCR_MASK for FZ16

[Richard Henderson]

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
Cc: address@hidden (3.0.1)
Reported-by: Laurent Desnogues <address@hidden>
Signed-off-by: Richard Henderson <address@hidden>
---
 target/arm/cpu.h    | 2 +-
 target/arm/helper.c | 5 +++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index 33d06f2340..0176716a70 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -1279,7 +1279,7 @@ 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/target/arm/helper.c b/target/arm/helper.c
index 64ff71b722..452d5e182a 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -11351,6 +11351,11 @@ 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;
-- 
2.17.1