linux-kernel - Re: [PATCH 2/3] MIPS: Add full ISA emulator.

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Date:	Thu, 4 Dec 2014 10:45:30 +0000
From:	Qais Yousef <qais.yousef@...tec.com>
To:	Paul Burton <paul.burton@...tec.com>,
	David Daney <ddaney@...iumnetworks.com>,
	Leonid Yegoshin <Leonid.Yegoshin@...tec.com>
CC:	David Daney <ddaney.cavm@...il.com>, <linux-mips@...ux-mips.org>,
	<ralf@...ux-mips.org>, <Zubair.Kakakhel@...tec.com>,
	<geert+renesas@...der.be>, <peterz@...radead.org>,
	<paul.gortmaker@...driver.com>, <macro@...ux-mips.org>,
	<chenhc@...ote.com>, <cl@...ux.com>, <mingo@...nel.org>,
	<richard@....at>, <zajec5@...il.com>, <james.hogan@...tec.com>,
	<keescook@...omium.org>, <tj@...nel.org>, <alex@...x-smith.me.uk>,
	<pbonzini@...hat.com>, <blogic@...nwrt.org>,
	<linux-kernel@...r.kernel.org>, <markos.chandras@...tec.com>,
	<dengcheng.zhu@...tec.com>, <manuel.lauss@...il.com>,
	<lars.persson@...s.com>, David Daney <david.daney@...ium.com>
Subject: Re: [PATCH 2/3] MIPS: Add full ISA emulator.

By all means I don't really understand the whole issues surrounding this 
but this approach looks better to me as well. It seems more generic and 
future proof and at least I can understand the patch series.

But did I say I don't understand all of this? Would be nice to hear from 
more people :)

Qais

On 12/04/2014 10:16 AM, Paul Burton wrote:
> Nice work David, I like this approach. It's so much simpler than hacking
> atop the current dsemul code. I also imagine this could be reused for
> emulation of instructions removed in r6, when running pre-r6 userland
> binaries on r6 systems.
>
> On Wed, Dec 03, 2014 at 06:21:36PM -0800, David Daney wrote:
>> On 12/03/2014 05:56 PM, Leonid Yegoshin wrote:
>>> I see only two technical issues here which differs:
>>>
>>> 1.  You believe your GCC experts, I trust HW Architecture manual and
>>> don't trust toolchain people too much ==> we see a different value in
>>> fact that your approach has a subset of emulated ISAs (and it can't, of
>>> course, emulate anything because some custom opcodes are reused).
>> Yes, I agree that the emulation approach cannot handle some of the cases you
>> mention (most would have to be the result of hand coded assembly
>> specifically trying to break it).
> I'm not sure I'd agree even with that - ASEs & vendor-specific
> instructions could easily be added if necessary.
>
> On Thu, Dec 04, 2014 at 05:56:51PM -0800, Leonid Yehoshin wrote:
>>> 2.  My approach is ready to use and is used right now, you still have a
>>> framework which passed an initial boot.
> Subjective.
>
> Thanks,
>      Paul

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