From: Huacai Chen <chenhuacai@kernel.org>
To: David Laight <David.Laight@aculab.com>
Cc: WANG Xuerui <kernel@xen0n.name>,
Huacai Chen <chenhuacai@loongson.cn>,
"loongarch@lists.linux.dev" <loongarch@lists.linux.dev>,
Xuefeng Li <lixuefeng@loongson.cn>,
Tiezhu Yang <yangtiezhu@loongson.cn>, Guo Ren <guoren@kernel.org>,
Jiaxun Yang <jiaxun.yang@flygoat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH V2] LoongArch: Add unaligned access support
Date: Tue, 18 Oct 2022 17:36:45 +0800 [thread overview]
Message-ID: <CAAhV-H42_dNyfYHDpdmPM=kG=VTF8xtPHMn-ojWHNkLnTNVDiQ@mail.gmail.com> (raw)
In-Reply-To: <cbbc32d4bb0f445197eb5d84d796595c@AcuMS.aculab.com>
On Tue, Oct 18, 2022 at 3:48 PM David Laight <David.Laight@aculab.com> wrote:
>
> From: Huacai Chen
> > Sent: 18 October 2022 08:33
> ...
> > > What about my more structured approach in another reply that avoids the
> > > huge else-if conditions? Both the terrible line wraps and codegen could
> > > be avoided.
> ...
> > OK, let me try.
>
> I suspect you can mask out some 'operand size' bits from the
> instructions - instead of checking each opcode.
>
> I'm also pretty sure you can't assume the FP register are live.
> If a read from userspace faults then there can be a full
> process switch - so by the time you try to write to the
> FP registers they no longer belong to the current process.
>
> It might be safer and simpler to just enforce the FP
> registers be saved and then act on the save area.
> I'd guess they get restored in the 'return to userspace'
> code.
Good catch, will be fixed in V4.
Huacai
>
> David
>
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2022-10-18 9:37 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-17 2:23 [PATCH V2] LoongArch: Add unaligned access support Huacai Chen
2022-10-17 4:22 ` Jinyang He
2022-10-17 7:37 ` Huacai Chen
2022-10-17 6:07 ` WANG Xuerui
2022-10-17 7:40 ` Huacai Chen
2022-10-17 8:59 ` Rui Wang
2022-10-17 9:03 ` Huacai Chen
2022-10-17 9:19 ` WANG Xuerui
2022-10-17 12:58 ` David Laight
2022-10-18 2:24 ` Huacai Chen
2022-10-18 3:29 ` WANG Xuerui
2022-10-18 7:32 ` Huacai Chen
2022-10-18 7:48 ` David Laight
2022-10-18 8:09 ` WANG Xuerui
2022-10-18 9:36 ` Huacai Chen [this message]
2022-10-17 14:19 ` kernel test robot
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