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target-arm: Add WFx instruction trap support 

Add support for trapping WFI and WFE instructions to the proper EL when
SCTLR/SCR/HCR settings apply.

Signed-off-by: Greg Bellows <greg.bellows@linaro.org>
[PMM: removed unnecessary tweaking of syn_wfx() prototype;
 use raise_exception();
 don't trap on WFE (and add comment explaining why not);
 remove unnecessary ARM_FEATURE checks;
 trap to EL3, not EL1, if in S-EL0 and SCTLR check fires]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
This commit is contained in:
Greg Bellows 2015-05-29 11:28:53 +01:00 committed by Peter Maydell
parent 84549b6dcf
commit b1eced713d
1 changed files with 59 additions and 1 deletions
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60
target-arm/op_helper.c
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@ -248,9 +248,60 @@ uint32_t HELPER(usat16)(CPUARMState *env, uint32_t x, uint32_t shift)
return res;
}
/* Function checks whether WFx (WFI/WFE) instructions are set up to be trapped.
* The function returns the target EL (1-3) if the instruction is to be trapped;
* otherwise it returns 0 indicating it is not trapped.
*/
static inline int check_wfx_trap(CPUARMState *env, bool is_wfe)
{
int cur_el = arm_current_el(env);
uint64_t mask;
/* 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.
*/
if (cur_el < 1 && arm_feature(env, ARM_FEATURE_V8)) {
int target_el;
mask = is_wfe ? SCTLR_nTWE : SCTLR_nTWI;
if (arm_is_secure_below_el3(env) && !arm_el_is_aa64(env, 3)) {
/* Secure EL0 and Secure PL1 is at EL3 */
target_el = 3;
} else {
target_el = 1;
}
if (!(env->cp15.sctlr_el[target_el] & mask)) {
return target_el;
}
}
/* We are not trapping to EL1; trap to EL2 if HCR_EL2 requires it
* No need for ARM_FEATURE check as if HCR_EL2 doesn't exist the
* bits will be zero indicating no trap.
*/
if (cur_el < 2 && !arm_is_secure(env)) {
mask = (is_wfe) ? HCR_TWE : HCR_TWI;
if (env->cp15.hcr_el2 & mask) {
return 2;
}
}
/* We are not trapping to EL1 or EL2; trap to EL3 if SCR_EL3 requires it */
if (cur_el < 3) {
mask = (is_wfe) ? SCR_TWE : SCR_TWI;
if (env->cp15.scr_el3 & mask) {
return 3;
}
}
return 0;
}
void HELPER(wfi)(CPUARMState *env)
{
CPUState *cs = CPU(arm_env_get_cpu(env));
int target_el = check_wfx_trap(env, false);
if (cpu_has_work(cs)) {
/* Don't bother to go into our "low power state" if
@ -259,6 +310,11 @@ void HELPER(wfi)(CPUARMState *env)
return;
}
if (target_el) {
env->pc -= 4;
raise_exception(env, EXCP_UDEF, syn_wfx(1, 0xe, 0), target_el);
}
cs->exception_index = EXCP_HLT;
cs->halted = 1;
cpu_loop_exit(cs);
@ -269,7 +325,9 @@ void HELPER(wfe)(CPUARMState *env)
CPUState *cs = CPU(arm_env_get_cpu(env));
/* Don't actually halt the CPU, just yield back to top
* level loop
* level loop. This is not going into a "low power state"
* (ie halting until some event occurs), so we never take
* a configurable trap to a different exception level.
*/
cs->exception_index = EXCP_YIELD;
cpu_loop_exit(cs);