linux-kernel - Re: [PATCH 2/3] loongarch: Introduce sys_loongarch_flush

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Message-Id: <f8769713-d9a4-4057-8df5-f1ea57707ebc@app.fastmail.com>
Date: Sat, 04 Jan 2025 11:18:17 +0000
From: "Jiaxun Yang" <jiaxun.yang@...goat.com>
To: "Jinyang Shen" <shenjinyang@...ngson.cn>,
 "Huacai Chen" <chenhuacai@...nel.org>, "Xuerui Wang" <kernel@...0n.name>
Cc: "Arnd Bergmann" <arnd@...db.de>, loongarch@...ts.linux.dev,
 linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH 2/3] loongarch: Introduce sys_loongarch_flush_icache syscall



在2025年1月4日一月 上午9:04，Jinyang Shen写道：
[...]
>>   
>> -# No special ABIs on loongarch so far
>> -syscall_abis_64 +=
>> +syscall_abis_64 += loongarch
>
> LoongArch64 need arch-specific syscall, but LoongArch32 needn't?

My bad, lost in rebasing :-)

>
[...]
>> diff --git a/scripts/syscall.tbl b/scripts/syscall.tbl
>> index ebbdb3c42e9f74613b003014c0baf44c842bb756..723fe859956809f26d6ec50ad7812933531ef687 100644
>> --- a/scripts/syscall.tbl
>> +++ b/scripts/syscall.tbl
>> @@ -298,6 +298,8 @@
>>   244	csky	set_thread_area			sys_set_thread_area
>>   245	csky	cacheflush			sys_cacheflush
>>   
>> +259	loongarch       loongarch_flush_icache	sys_loongarch_flush_icache
>
> Can we use cacheflush as arc, csky and nios2?

I think cacheflush syscall is more or less an outdated design inherited
from...MIPS...

Exposing flush of other cache levels to user space is not wise in security
perspective. The design of cacheflush syscall is also not vDSO friendly.
riscv_flush_icache is designed to avoid those drawbacks, and we should follow.

Thanks

>
> Jinyang
>
[...]

-- 
- Jiaxun