Re: Did the "TCG" emulation mode has a full capability compare with the "KVM" emulation mode?

["Alex Bennée" <alex.bennee@linaro.org>]

tugouxp  <13824125580@163.com> writes:

> Thank you!
>
> BTW, TCG also has two backends implemention, 1. Native host arch tranlation. and 2. TCI byte code interpreter. The
> difference is that the first one will tranlation the target arch code to host arch instrtions and then executed in host cpu. but
> the latter is a high level interperation. compare these two backends, Are there any capability difference on the system
> emulation about the two backends? thank you.

No - TCI is just a slower fallback to interpret TCG ops directly
compared to executing JITed code.

>
> At 2024-06-24 16:57:40, "Alex Bennée" <alex.bennee@linaro.org> wrote:
>>tugouxp <13824125580@163.com> writes:
>>
>>> Hello folks:
>>>    I have a puzzle on qemu major two emuation implentions on whole system emulation, that is ,except the emuation speed,
>>> did the TCG work mode has any weakness than "KVM" work mode on whole system emulations(including kernek and
>>> user-space)?
>>
>>It depends on the guest architecture. Some are more complete than
>>others. The x86 emulation for example doesn't cover all the modern x86
>>extensions although there have been some improvements to its vector
>>handling recently.
>>
>>One thing TCG can do that KVM can't is emulate code running at higher
>>priority than kernel-mode. For example for ARM we can emulate the
>>EL3/Root domain and secure and confidential realms. In KVM you can only
>>run a guest EL1 kernel and its user space.
>>
>>> is there any work that kvm can do but TCG cant? 
>>>
>>> of course kvm is much faster than TCG, but my question just about the funtion, not care about speed.
>>>
>>> thanks for your kindly help!
>>> BRs
>>> zilong.
>>
>>-- 
>>Alex Bennée
>>Virtualisation Tech Lead @ Linaro

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro