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From: Richard Henderson <rth@twiddle.net>
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Date: Thu, 3 Aug 2017 13:46:56 -0700
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Subject: Re: [Qemu-devel] [Qemu-arm] [PATCH 02/15] target/arm: Don't trap
 WFI/WFE for M profile
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To: "Edgar E. Iglesias" <edgar.iglesias@gmail.com>
Cc: Peter Maydell <peter.maydell@linaro.org>, qemu-arm@nongnu.org, qemu-devel@nongnu.org, patches@linaro.org

On 08/03/2017 01:40 PM, Edgar E. Iglesias wrote:
> I don't have the spec at hand but IIRC the trap should only happen
> if the processor would have entered the low-power state (i.e if
> there's no work).

  when SystemHintOp_WFE
    if IsEventRegisterSet() then
      ClearEventRegister();
    else
      if PSTATE.EL == EL0 then
        AArch64.CheckForWFxTrap(EL1, TRUE);
      if HaveEL(EL2) && !IsSecure()
         && PSTATE.EL IN {EL0, EL1} && !IsInHost() then
        AArch64.CheckForWFxTrap(EL2, TRUE);
      if HaveEL(EL3) && PSTATE.EL != EL3 then
        AArch64.CheckForWFxTrap(EL3, TRUE);
      WaitForEvent();

Ah, I see what you mean, since WaitForEvent is also
described as checking EventRegister.

Thanks.


r~