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Date: Mon, 26 Nov 2018 20:38:25 -0500
From: "Emilio G. Cota" <cota@braap.org>
Message-ID: <20181127013825.GE22108@flamenco>
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Subject: Re: [Qemu-devel] [RFC 23/48] translator: add plugin_insn argument
 to translate_insn
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To: Richard Henderson <richard.henderson@linaro.org>
Cc: Alex =?iso-8859-1?Q?Benn=E9e?= <alex.bennee@linaro.org>, Stefan Hajnoczi <stefanha@gmail.com>, Peter Maydell <peter.maydell@linaro.org>, qemu-devel@nongnu.org, Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>, =?iso-8859-1?Q?Llu=EDs?= Vilanova <vilanova@ac.upc.edu>

On Mon, Nov 26, 2018 at 11:30:25 -0800, Richard Henderson wrote:
> On 11/26/18 11:07 AM, Emilio G. Cota wrote:
> > The main reason why I added the qemu_plugin_insn_append calls
> > was to avoid reading the instructions twice from guest memory,
> > because I was worried that doing so might somehow alter the
> > guest's execution, e.g. what if we read a cross-page instruction,
> > and both pages mapped to the same TLB entry? We'd end up having
> > more TLB misses because instrumentation was enabled.
> 
> A better solution for this, I think is to change direct calls from
> 
>   cpu_ldl_code(env, pc);
> to
>   translator_ldl_code(dc_base, env, pc);
> 
> instead of passing around a new argument separate from DisasContextBase?

I think this + diff'ing pc_next should work to figure out the
contents and size of each instruction.

I'll do it this way in v2.

Thanks,

		Emilio