Re: [PATCH for-5.1 V4 0/7] mips: Add Loongson-3 machine support (with KVM)

[Aleksandar Markovic]

11:06 Pet, 05.06.2020. Jiaxun Yang <jiaxun.yang@flygoat.com> је написао/ла:
>
> On Fri, 5 Jun 2020 10:38:36 +0200
> Aleksandar Markovic <aleksandar.qemu.devel@gmail.com> wrote:
>
> > уто, 2. јун 2020. у 04:38 Huacai Chen <zltjiangshi@gmail.com> је
> > написао/ла:
> > >
> > > Loongson-3 CPU family include Loongson-3A R1/R2/R3/R4 and
> > > Loongson-3B R1/R2. 
> >
> > Hi, Huacai,
> >
> > The documents you kindly provided contain some valuable info on
> > Loongson-3A R1/R2/R3/R4 and Loongson-3B R1/R2. However, I
> > couldn't find detailed instruction-by-instruction specifications.
> >
> > In fact, I don't need all the details right now, but some form of
> > overview of instructions sets of Loongson-3A R1/R2/R3/R4 and
> > Loongson-3B R1/R2. Could you please provide textual description
> > (one of two paragraph) of supported instructions for each of these
> > models:
> >
>
> Hi Aleksandar,
>
> I'm going to explain this according to the names of vendor specified
> ASEs name in GCC & Binutils.
>
> There are some instruction that not covered by public documents, that's
> out of our scope so I'm not going to talk them.
>
> Firstly, there are some ASEs not being upstreamed yet:
>  - Loongson-AMO (Atomic Opreations, Looks like RISC-V)
>  - Loongson-EXT3 (Loongson Extention 3)
>  - Loongson-CSR (Core Status Registers, instructions to read some
>    private core register, including something called "stable-counter"
>    (TSC like timer) and CPUCFG(something like cpuid in x86))
>
>  - MIPS-MSA-Ctypto (Including AES, SHA, MD5 stuff)
>  - MIPS MSA2 (256-bit MSA instructions)
>
> And there is a ASE that only being used in kernel so not even being
> mentioned in toolchain.
>  - Loongson-SPW (LWPTE, LDPTE used to help with pagetable walking)
>
> ALl these processors have mips64r2 as baseline.
>
> > * Loongson-3A R1
> Loongson-MMI, Loongson-EXT
>
> > * Loongson-3A R2
> Loongson-MMI, Loongson-EXT, Looongson-EXT2, Loongson-SPW, DSP, DSPr2
>
> > * Loongson-3A R3
> Same as R2. This revision mainly focus on bugfix and improve clock
> speed.
>
> > * Loongson-3A R4
> Loongson-MMI, Loongson-EXT, Looongson-EXT2, Loongson-SPW, Loongson-AMO,
> Loongson-EXT3, Loongson-CSR, MSA Crypto, MSA2
>
> This processor even support hardware unaligned accessing.
>
> > * Loongson-3B R1
> > * Loongson-3B R2
> Loongson-3B R1 and R2 are mostly identical with Loongson-3A R1, the
> difference is it have 8-cores in a package. It was designed for HPC so
> there are some domain specific SIMD instructions, but they're not
> available to public.
>
> And a new family member of Loongson64:
> Loongson-2K (R1):
> Loongson-MMI, Loongson-EXT, Looongson-EXT2, MSA.
>

Thanks for your detailed response, Juaxun.

I will think over the weekend about the new aspects you mentioned here. All this is valuable info for long-term planning. But also in short-term - for this very series. Expect my answer early next week.

Best Regards and Best Health!

Aleksandar

> >
> > (what is the base instructuin set; the difference to the previous
> > model; what SIMD extension (LMI/MSA) is supported other specifics
> > around supported instructions)
> >
> > Based on your answer I may bring forward some suggestions on the
> > improvement of v4 of this series.
> >
> > Truly yours,
> > Aleksandar
> >
>
> Thank a lot.
>
> - Jiaxun