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From: "Pavel Dovgaluk" <Pavel.Dovgaluk@ispras.ru>
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Date: Wed, 13 May 2015 09:57:23 +0300
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Subject: Re: [Qemu-devel] when does a target frontend need to use
	gen_io_start()/gen_io_end() ?
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To: 'Paolo Bonzini' <pbonzini@redhat.com>, 'Peter Maydell' <peter.maydell@linaro.org>, 'QEMU Developers' <qemu-devel@nongnu.org>
Cc: 'Richard Henderson' <rth@twiddle.net>

> From: Paolo Bonzini [mailto:paolo.bonzini@gmail.com] On Behalf Of Paolo Bonzini
> On 12/05/2015 17:32, Peter Maydell wrote:
> > In order for -icount to work, it's important for the target
> > translate.c code to correctly bracket any generated code which
> > can "do I/O" with gen_io_start()/gen_io_end() calls. But
> > does anybody know exactly what the criteria are here for this?
> > It would be nice if we could document this in a comment in
> > gen_icount.h -- I'm happy to write one up if somebody will just
> > tell me what the right answer is :-)
> 
> It's any instruction that can cause an icount read, typically through
> QEMU_CLOCK_VIRTUAL or cpu_get_ticks().

Doesn't this mean that ARM has incorrect implementation of icount?
MMIO is common for this platform, but none of memory accesses are
surrounded with gen_io_start()/gen_io_end().

Pavel Dovgalyuk