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From: "Pavel Dovgalyuk" <dovgaluk@ispras.ru>
References: <20181005154910.3099-1-alex.bennee@linaro.org>
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Date: Mon, 29 Oct 2018 15:24:26 +0300
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Subject: Re: [Qemu-devel] [RFC PATCH  00/21] Trace updates and plugin RFC
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To: =?utf-8?Q?'Alex_Benn=C3=A9e'?= <alex.bennee@linaro.org>
Cc: qemu-devel@nongnu.org, Pavel.Dovgaluk@ispras.ru, vilanova@ac.upc.edu, cota@braap.org

> From: Alex Benn=C3=A9e [mailto:alex.bennee@linaro.org]
> Pavel Dovgalyuk <dovgaluk@ispras.ru> writes:
> > One more question about your trace points.
> > In case of using trace point on every instruction execution, we may =
need
> > accessing vCPU registers (including the flags). Are they valid in =
such
> > cases?
>=20
> They are probably valid but the tricky bit will be doing it in a way
> that doesn't expose the internals of the TCG. Maybe we could exploit =
the
> GDB interface for this or come up with a named referencex API.
>=20
> > I'm asking, because at least i386 translation optimizes writebacks.
>=20
> How so? I have to admit the i386 translation code is the most opaque =
to
> me but I wouldn't have thought changing the semantics of the guests
> load/store operations would be a sensible idea.

Writeback to the registers (say EFLAGS), not to the memory.

Pavel Dovgalyuk