linux-kernel - Re: use of setjmp/longjmp in x86 emulator.

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Date:	Mon, 1 Mar 2010 14:52:23 +0200
From:	Gleb Natapov <gleb@...hat.com>
To:	Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, avi@...hat.com,
	mtosatti@...hat.com, zamsden@...hat.com
Subject: Re: use of setjmp/longjmp in x86 emulator.

On Mon, Mar 01, 2010 at 09:45:46PM +0900, Takuya Yoshikawa wrote:
> Gleb Natapov wrote:
> >I am looking at improving KVM x86 emulator. Current code does not
> 
> Does your plan also include making the emulator independent of KVM?
Yes, I am planning to make it more independent from KVM that it is now
(by adding more callbacks to x86_emulate_ops).

> Could you tell me about the future plan if possible?
> 
We saw a lot of problems and shortcomings in the emulator recently, so
the plan is to improve its correctness. There is also a requirement to be
able single step emulated code. Having setjmp/longjmp will greatly simplify
the code. What are you interested in?

> >handle some special cases correctly (code execution from ROM, ins/outs
> >to/from MMIO) and many exception conditions during instruction emulation
> >are not handled correctly. There is a lot of code in emulator that is
> >there only for exception propagation. Using setjmp/longjmp will be very
> >beneficial here as exception condition during instruction execution
> >maps very naturally to setjmp/longjmp, so my question is what about
> >adding setjmp/longjmp implementation to the kernel, or alternatively,
> >if there is a fear that it can be abused, add it locally to emulator.c?
> >Note that instruction emulation is always done in process context.
> >
> >--
> >			Gleb.
> >--
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--
			Gleb.
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