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From: Sergey Fedorov <serge.fdrv@gmail.com>
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Date: Tue, 12 Apr 2016 15:48:21 +0300
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Subject: Re: [Qemu-devel] [RFC v2 08/11] tcg: add options for enabling MTTCG
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To: =?UTF-8?Q?Alex_Benn=c3=a9e?= <alex.bennee@linaro.org>
Cc: mttcg@listserver.greensocs.com, fred.konrad@greensocs.com, a.rigo@virtualopensystems.com, cota@braap.org, qemu-devel@nongnu.org, mark.burton@greensocs.com, pbonzini@redhat.com, jan.kiszka@siemens.com, rth@twiddle.net, peter.maydell@linaro.org, claudio.fontana@huawei.com, Peter Crosthwaite <crosthwaite.peter@gmail.com>, =?UTF-8?Q?Andreas_F=c3=a4rber?= <afaerber@suse.de>

On 12/04/16 14:48, Alex Bennée wrote:
> Sergey Fedorov <serge.fdrv@gmail.com> writes:
>
>> On 05/04/16 18:32, Alex Bennée wrote:
>>> diff --git a/qemu-options.hx b/qemu-options.hx
>>> index a770086..4eca704 100644
>>> --- a/qemu-options.hx
>>> +++ b/qemu-options.hx
>>> @@ -3224,6 +3224,20 @@ Attach to existing xen domain.
>>>  xend will use this when starting QEMU (XEN only).
>>>  ETEXI
>>>
>>> +DEF("tcg", HAS_ARG, QEMU_OPTION_tcg, \
>>> +    "-tcg [mttcg=on|off] control TCG options\n", QEMU_ARCH_ALL)
>>> +STEXI
>>> +@item -tcg
>>> +@findex -tcg
>>> +@table @option
>>> +@item mttcg=[on|off]
>>> +Control multi-threaded TCG. By default QEMU will enable multi-threaded
>>> +emulation for front/back-end combinations that are known to work. The
>>> +user may enable it against the defaults however odd guest behaviour
>>> +may occur.
>>> +@end table
>>> +ETEXI
>> Maybe we'd better use existing qemu accelerator framework and introduce
>> "-machine accel=mttcg" option?
> My worry would be breaking existing code which assumes kvm | tcg. We
> will want to enable mttcg by default for combos that work without having
> to tweak tooling that already uses the -machine options.

You are right, we'd better make MTTCG as an option for TCG, not as a
separate accelerator.

Kind regards,
Sergey