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[Qemu-arm] [PATCH 02/15] target/arm: Don't trap WFI/WFE for M profile


From: Peter Maydell
Subject: [Qemu-arm] [PATCH 02/15] target/arm: Don't trap WFI/WFE for M profile
Date: Wed, 2 Aug 2017 17:43:48 +0100

M profile cores can never trap on WFI or WFE instructions. Check for
M profile in check_wfx_trap() to ensure this.

The existing code will do the right thing for v7M cores because
the hcr_el2 and scr_el3 registers will be all-zeroes and so we
won't attempt to trap, but when we start setting ARM_FEATURE_V8
for v8M cores the v8A handling of SCTLR.nTWE and .nTWI will not
give the right results.

Signed-off-by: Peter Maydell <address@hidden>
---
 target/arm/op_helper.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/target/arm/op_helper.c b/target/arm/op_helper.c
index 2a85666..5a94a5f 100644
--- a/target/arm/op_helper.c
+++ b/target/arm/op_helper.c
@@ -370,6 +370,11 @@ static inline int check_wfx_trap(CPUARMState *env, bool 
is_wfe)
     int cur_el = arm_current_el(env);
     uint64_t mask;
 
+    if (arm_feature(env, ARM_FEATURE_M)) {
+        /* M profile cores can never trap WFI/WFE. */
+        return 0;
+    }
+
     /* If we are currently in EL0 then we need to check if SCTLR is set up for
      * WFx instructions being trapped to EL1. These trap bits don't exist in 
v7.
      */
-- 
2.7.4




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