Re: Assessment of the difficulty in porting CPU architecture for qemu

Re: Assessment of the difficulty in porting CPU architecture for qemu

[Alistair Francis]

On Fri, Nov 17, 2023 at 5:35 PM 方 <1584389042@qq.com> wrote:
>
>  Hello everyone! I am working on implementing a tool to assess the complexity of CPU architecture porting. It primarily focuses on RISC-V architecture porting. In fact, the tool may have an average estimate of various architecture porting efforts.My focus is on the overall workload and difficulty of transplantation in the past and future,even if a project has already been ported.As part of my dataset, I have collected the **qemu** project. **I would like to gather community opinions to support my assessment. I appreciate your help and response!** Based on scanning tools, the porting complexity is determined to be high, with a significant amount of code related to the CPU architecture in the project.  Is this assessment accurate?Do you have any opinions on personnel allocation and consumption time？ I look forward to your help and response.

The people who did the original QEMU RISC-V port aren't involved any more.

You are correct that QEMU is significantly complex to port to a new
architecture compared to most other userspace software. I think it
would be similar to other JIT software in that regard.

Alistair

Re: Assessment of the difficulty in porting CPU architecture for qemu

[Peter Maydell]

On Fri, 17 Nov 2023 at 07:35, 方 <1584389042@qq.com> wrote:
>
>  Hello everyone! I am working on implementing a tool to assess the complexity of CPU architecture porting. It primarily focuses on RISC-V architecture porting. In fact, the tool may have an average estimate of various architecture porting efforts.My focus is on the overall workload and difficulty of transplantation in the past and future,even if a project has already been ported.As part of my dataset, I have collected the **qemu** project. **I would like to gather community opinions to support my assessment. I appreciate your help and response!** Based on scanning tools, the porting complexity is determined to be high, with a significant amount of code related to the CPU architecture in the project.

You should be careful here to distinguish the code in QEMU
which is related to handling RISC-V as a *guest* architecture
(i.e. one which QEMU emulates) from the code which is related
to handling RISC-V as a *host* architecture. For purposes of
"porting QEMU to a RISC-V host", only the latter complexity counts.
The former we would have to do anyway, even if QEMU only ever
ran on x86-64 machines. You should check whether your scanner
has correctly figured this out.

-- PMM