Re: [PATCH v6 00/21] Add LoongArch linux-user emulation support

[gaosong]

Hi, Xuerui.

> -----Original Messages-----
&gt; From: "WANG Xuerui" <i.qemu@xen0n.name>
&gt; Sent Time: 2021-09-22 17:49:56 (Wednesday)
&gt; To: "Song Gao" <gaosong@loongson.cn>, "Richard Henderson" 
<richard.henderson@linaro.org>, qemu-devel@nongnu.org
&gt; Cc: peter.maydell@linaro.org, thuth@redhat.com, philmd@redhat.com, 
yangxiaojuan@loongson.cn, laurent@vivier.eu, peterx@redhat.com, 
f4bug@amsat.org, alistair.francis@wdc.com, maobibo@loongson.cn, 
pbonzini@redhat.com, bmeng.cn@gmail.com, alex.bennee@linaro.org, 
chenhuacai@loongson.cn
&gt; Subject: Re: [PATCH v6 00/21] Add LoongArch linux-user emulation support
&gt; 
&gt; Hi Song,
&gt; 
&gt; On 9/22/21 14:22, Song Gao wrote:
&gt; &gt; Hi, Richard.
&gt; &gt;
&gt; &gt; On 09/21/2021 05:17 AM, Richard Henderson wrote:
&gt; &gt;&gt; On 9/17/21 1:12 AM, Song Gao wrote:
&gt; &gt;&gt;&gt; The 'o32' code has been deleted at the latest kernel [1]. 
This series only support
&gt; &gt;&gt;&gt; linux-user emulation.
&gt; &gt;&gt; I have now reviewed all but the linux-user/ portion.
&gt; &gt;&gt;
&gt; &gt; Thank you!
&gt; &gt;&gt; I see that kernel upstreaming is in progress,
&gt; &gt;&gt;
&gt; &gt;&gt; 
https://lore.kernel.org/linux-kernel/20210917035736.3934017-1-chenhuacai@loongson.cn/
&gt; &gt;&gt;
&gt; &gt;&gt; so hopefully this will be resolved soon.
&gt; &gt;&gt;
&gt; &gt;&gt; Have you started working on system mode support for LoongArch, so 
that one may run that kernel?
&gt; &gt;&gt; Yes. We already support running the old kernel, but we don't 
support running the latest kernel yet.
&gt; 
&gt; (the reply was at the wrong quotation level, never mind though)
&gt; 
&gt; First of all, thanks for your contribution and continued engagement with 
&gt; the wider development community! That's what it takes to unlock the 
&gt; 3A5000 and future products' so many possibilities.
&gt; 
&gt; As for the system emulation part, I have some questions though:
&gt; 
&gt; - How would you provide the necessary firmware bits? Ideally that would 
&gt; be some open-source reference implementation so people would be able to 
&gt; collaborate on that front, and to maybe customize for specialized needs 
&gt; (e.g. ultra-dense cloud use cases like with Firecracker).
&gt; 

On QEMU, we only support 64 bit, So far, we have no plan to support 32 bit.

As far as I know, LoongArch BIOS is planning to open source.

&gt; - How is old/new kernel ABI affecting your system-level emulation 
&gt; compatibility? IIUC the underlying ISA and chip behavior should be the 
&gt; same, only difference would be the firmware-kernel ABI, but again it 
&gt; should be just a matter of substituting the right image.
&gt;

We only supoort the lastet kernel [1].

[1] https://github.com/loongson/linux/tree/loongarch-next

&gt; - Would the resulting work support emulating both old-world and 
&gt; new-world systems? AFAIK those commercial distros who're VERY early 
&gt; adopters of LoongArch are given similarly early toolchains/kernels. They 
&gt; belong to the old-world as a result, and are very likely to be stuck on 
&gt; the old-world ABI for whole major versions before migrating, if at all 
&gt; possible. Closed-source/commercial software also risk being available 
&gt; only for the old-world, and it would be extremely important to provide 
&gt; some degree of interoperability so that we don't split the ecosystem.

On the basis of supporting the latest kernel, we will try to be compatible with 
the old version of LoongArch. 
But the result may be incompatible。

Song Gao
thanks.

&gt; Questions aside, you did a nice work so far; looking forward to your 
&gt; system emulation work!
</richard.henderson@linaro.org></gaosong@loongson.cn></i.qemu@xen0n.name>

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