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From: Peter Maydell <peter.maydell@linaro.org>
Date: Thu, 23 Apr 2015 15:51:48 +0100
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Subject: Re: [Qemu-devel] [PATCH v2 9/9] target-arm: Add WFx instruction
	trap support
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To: Greg Bellows <greg.bellows@linaro.org>
Cc: "Edgar E. Iglesias" <edgar.iglesias@gmail.com>, =?UTF-8?B?QWxleCBCZW5uw6ll?= <alex.bennee@linaro.org>, QEMU Developers <qemu-devel@nongnu.org>, Sergey Fedorov <serge.fdrv@gmail.com>

On 23 April 2015 at 15:41, Greg Bellows <greg.bellows@linaro.org> wrote:
> Ok it sounds like the primary concern is the performance impact of
> constantly trapping wfe to EL2 (in which case HCR must be set to cause
> this).  Should we still honor EL3 and EL1 trapping ofr wfe?  In other words
> check if they are the target and allow it if !has_work?

We should check what the architecture manual says, but I think
that in all the trap-WFE cases it says "traps if the CPU
would go into a low power state". QEMU *never* goes into a
low power state on WFE, so we never trap.

-- PMM