Re: [Qemu-devel] [Qemu-riscv] RISCV: when will the CLIC be ready?

[Chih-Min Chao]

On Mon, Aug 19, 2019 at 9:47 PM liuzhiwei <address@hidden> wrote:

>
> On 2019/8/17 上午1:29, Alistair Francis wrote:
> > On Thu, Aug 15, 2019 at 8:39 PM liuzhiwei<address@hidden>  wrote:
> >> Hi, Palmer
> >>
> >> When Michael Clark still was the maintainer of RISCV QEMU, he wrote in
> the mail list, "the CLIC interrupt controller is under testing,
> >> and will be included in QEMU 3.1 or 3.2". It is pity that the CLIC is
> not in
> >> included even in QEMU 4.1.0.
> > I see that there is a CLIC branch available here:
> > https://github.com/riscv/riscv-qemu/pull/157
> >
> > It looks like all of the work is in a single commit
> > (
> https://github.com/riscv/riscv-qemu/pull/157/commits/206d9ac339feb9ef2c325402a00f0f45f453d019
> )
> > and that most of the other commits in the PR have already made it into
> > master.
> >
> > Although the CLIC commit is very large it doesn't seem impossible to
> > manually pull out the CLIC bits and apply it onto master.
> >
> > Do you know the state of the CLIC model? If it's working it shouldn't
> > be too hard to rebase the work and get the code into mainline.
> >
> > Alistair
> >
> Hi,  Alistair
>
> In my opinion, the CLIC code almost works.
>
> Last year when my workmate ported an RTOS, I once read the CLIC
> specification and used the CLIC model code. It worked through  all the
> tests after fixed two bugs. I also had sent the patch to Michael, but
> without response(maybe a wrong email address).
>
> diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
> index 7bf6cbc..95d80ab 100644
> --- a/target/riscv/cpu_helper.c
> +++ b/target/riscv/cpu_helper.c
> @@ -505,6 +505,9 @@ static target_ulong riscv_intr_pc(CPURISCVState *env,
>       if (!(async || clic)) {
>           return tvec & ~0b11;
>       }
> +    if (clic) {
> +        cause &= 0x3ff;
> +    }
>
>       /* bits [1:0] encode mode; 0 = direct, 1 = vectored, 2 >= reserved */
>       switch (mode1) {
> @@ -645,6 +648,9 @@ void riscv_cpu_do_interrupt(CPUState *cs)
>           riscv_cpu_set_mode(env, PRV_M);
>       }
>
> +    if (clic) {
> +        env->exccode = 0;
> +    }
>       /* NOTE: it is not necessary to yield load reservations here. It is
> only
>          necessary for an SC from "another hart" to cause a load
> reservation
>          to be yielded. Refer to the memory consistency model section of
> the
>
> After that, the specification has updated and the code may changed. I
> didn't pull new code again.
>
> If the CLIC model may merged into the mainline, and no body maintain the
> code, I'd like to work on it, fixing the bugs and updating the code
> according to latest specification.
>
> Best Regards,
> Zhiwei
>
> >> As we have cpus using CLIC, I have to use the out of tree qemu code in
> SIFIVE
> >> a long time. Could you tell me when it will be upstreamed?
> >>
> >> Best Regards
> >> Zhiwei
> >>
>
>
Hi Zhiwei,

I think what Alistair point out is the latest clic version (or
https://github.com/riscv/riscv-qemu/tree/riscv-qemu-3.1).  The two
versions, on pull request and 3.1 branch, should be similar.
As far as I know, there is no concrete plan on CLIC patch in short term.
It is good to know that the clic patch has been run with real RTOS.
It is also great if you could update the implementation to latest spec and
send the patch again.

chihmin