linux-kernel - Re: [PATCH 2/2] MIPS: ebpf jit: Implement R4000 workarounds

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Message-Id: <c36effcb-5a5f-49b0-8bbe-cc46addf2959@app.fastmail.com>
Date:   Mon, 27 Feb 2023 15:47:05 +0000
From:   "Jiaxun Yang" <jiaxun.yang@...goat.com>
To:     "Maciej W. Rozycki" <macro@...am.me.uk>,
        "Johan Almbladh" <johan.almbladh@...finetworks.com>
Cc:     "linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>,
        linux-kernel@...r.kernel.org,
        "Thomas Bogendoerfer" <tsbogend@...ha.franken.de>,
        "paulburton@...nel.org" <paulburton@...nel.org>,
        bpf@...r.kernel.org, "Alexei Starovoitov" <ast@...nel.org>,
        "Andrii Nakryiko" <andrii@...nel.org>,
        "Daniel Borkmann" <daniel@...earbox.net>
Subject: Re: [PATCH 2/2] MIPS: ebpf jit: Implement R4000 workarounds



在2023年2月27日二月 下午3:18，Maciej W. Rozycki写道：
> On Mon, 27 Feb 2023, Johan Almbladh wrote:
>
>> > > R4000 is a 64-bit CPU, so the 32-bit JIT implementation will not be
>> > > used. From the Makefile:
>> > >
>> > > ifeq ($(CONFIG_32BIT),y)
>> > >        obj-$(CONFIG_BPF_JIT) += bpf_jit_comp32.o
>> > > else
>> > >        obj-$(CONFIG_BPF_JIT) += bpf_jit_comp64.o
>> > > endif
>> >
>> > It’s common practice to run 32-bit kernel on R4000 based systems to save some memory :-)
>> 
>> Ok, I understand.
>
>  Likewise:
>
> 	select CPU_R4000_WORKAROUNDS if 64BIT
> 	select CPU_R4400_WORKAROUNDS if 64BIT
>
> This only applies to 64-bit operations, which are not used in 32-bit code 
> (one reason why these early silicon revisions were originally used with 
> 32-bit software only).

Thanks for the info.
Will drop 32bit part from both patch.

>
>   Maciej

-- 
- Jiaxun