From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: Xi Ruoyao <xry111@xry111.site>
Cc: Huacai Chen <chenhuacai@kernel.org>,
WANG Xuerui <kernel@xen0n.name>,
linux-crypto@vger.kernel.org, loongarch@lists.linux.dev,
Jinyang He <hejinyang@loongson.cn>,
Tiezhu Yang <yangtiezhu@loongson.cn>,
Arnd Bergmann <arnd@arndb.de>
Subject: Re: [PATCH v4 1/4] LoongArch: vDSO: Wire up getrandom() vDSO implementation
Date: Tue, 27 Aug 2024 16:30:52 +0200 [thread overview]
Message-ID: <Zs3jHMxpR_jUFg9o@zx2c4.com> (raw)
In-Reply-To: <f404ae352a8cba3e035c9d5a10b553fb4497bb02.camel@xry111.site>
On Tue, Aug 27, 2024 at 10:26:53PM +0800, Xi Ruoyao wrote:
> > And then use addi.w here with the integer literals instead?
>
> LoongArch addi.w can only handle 12-bit signed immediate values (such a
> limitation is very common in RISC machines). On my processor I can
> avoid using a register to materialize the constant with addu16i.d +
> addu12i.w + addi.w. But there would be 3 instructions, and addu12i.w is
> a part of the Loongson Binary Translation extension which is not
> available on some processors. Also LBT isn't intended for general use,
> so most LBT instructions have a lower throughput than the basic
> instructions.
Very interesting, thanks for the explanation.
Jason
next prev parent reply other threads:[~2024-08-27 14:31 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-08-27 13:20 [PATCH v4 0/4] LoongArch: Implement getrandom() in vDSO Xi Ruoyao
2024-08-27 13:20 ` [PATCH v4 1/4] LoongArch: vDSO: Wire up getrandom() vDSO implementation Xi Ruoyao
2024-08-27 13:36 ` Xi Ruoyao
2024-08-27 13:49 ` Jason A. Donenfeld
2024-08-27 14:26 ` Xi Ruoyao
2024-08-27 14:30 ` Jason A. Donenfeld [this message]
2024-08-27 15:07 ` Xi Ruoyao
2024-08-28 14:26 ` Jason A. Donenfeld
2024-08-28 14:33 ` Jason A. Donenfeld
2024-08-27 13:20 ` [PATCH v4 2/4] selftests/vDSO: Add --cflags for pkg-config command querying libsodium Xi Ruoyao
2024-08-27 13:54 ` Jason A. Donenfeld
2024-08-27 13:20 ` [PATCH v4 3/4] selftests/vDSO: Use KHDR_INCLUDES to locate UAPI headers for vdso_test_getrandom Xi Ruoyao
2024-08-27 13:58 ` Jason A. Donenfeld
2024-08-27 14:07 ` LEROY Christophe
2024-08-27 14:15 ` Jason A. Donenfeld
2024-08-27 14:41 ` Xi Ruoyao
2024-08-27 14:50 ` Christophe Leroy
2024-08-27 15:00 ` Jason A. Donenfeld
2024-08-27 15:05 ` Xi Ruoyao
2024-08-27 15:10 ` Jason A. Donenfeld
2024-08-27 15:28 ` Xi Ruoyao
2024-08-27 15:29 ` Jason A. Donenfeld
2024-08-28 11:36 ` Jason A. Donenfeld
2024-08-28 12:00 ` Xi Ruoyao
2024-08-27 15:12 ` Christophe Leroy
2024-08-27 13:20 ` [PATCH v4 4/4] selftests/vDSO: Enable vdso getrandom tests for LoongArch Xi Ruoyao
2024-08-27 14:00 ` Jason A. Donenfeld
2024-08-27 14:45 ` Xi Ruoyao
2024-08-27 13:51 ` [PATCH v4 0/4] LoongArch: Implement getrandom() in vDSO Jason A. Donenfeld
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