From: Huacai Chen <chenhuacai@kernel.org>
To: Jinyang He <hejinyang@loongson.cn>
Cc: Huacai Chen <chenhuacai@loongson.cn>,
loongarch@lists.linux.dev, Xuefeng Li <lixuefeng@loongson.cn>,
Tiezhu Yang <yangtiezhu@loongson.cn>, Guo Ren <guoren@kernel.org>,
Xuerui Wang <kernel@xen0n.name>,
Jiaxun Yang <jiaxun.yang@flygoat.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH V2] LoongArch: Add unaligned access support
Date: Mon, 17 Oct 2022 15:37:15 +0800 [thread overview]
Message-ID: <CAAhV-H54TeCwuUu+pGyGUDgy3_k1eCA1hX56-ZrTuk2_WRiFxQ@mail.gmail.com> (raw)
In-Reply-To: <67d9acd0-692f-95d4-2c92-4e43e1d0100c@loongson.cn>
Hi, Jinyang,
On Mon, Oct 17, 2022 at 12:22 PM Jinyang He <hejinyang@loongson.cn> wrote:
>
> Hi, Huacai,
>
>
> On 2022/10/17 上午10:23, Huacai Chen wrote:
> > [...]
> > + default:
> > + panic("unexpected fd '%d'", fd);
> Due to the optimization of gcc, the panic() is unused actually and leave
> the symbol 'read/write_fpr' in vmlinux. Maybe we can use unreachable() and
>
> always_inline.
Seems impossible, I have tried __always_inline() and BUILD_BUG(), then
BUILD_BUG() is triggered, because the reg-number is not a compile time
constant.
>
> > [...]
> > +
> > +fault:
> > + /* roll back jump/branch */
> > + regs->csr_era = origpc;
> > + regs->regs[1] = origra;
>
> I'm not sure where the csr_era and regs[1] was damaged...
Yes, seems not be damaged.
>
> > [...]
> >
> > +/*
> > + * unsigned long unaligned_read(void *addr, void *value, unsigned long n, bool sign)
> > + *
> > + * a0: addr
> > + * a1: value
> > + * a2: n
> > + * a3: sign
> > + */
> > +SYM_FUNC_START(unaligned_read)
> > + beqz a2, 5f
> > +
> > + li.w t1, 8
> IMHO we can avoid the constant reg t1.
OK, thanks.
> > + li.w t2, 0
> > +
> > + addi.d t0, a2, -1
> > + mul.d t1, t0, t1
> > + add.d a0, a0, t0
> > +
> > + beq a3, zero, 2f
> beqz
OK, thanks.
> > +1: ld.b t3, a0, 0
> > + b 3f
> > +
> > +2: ld.bu t3, a0, 0
> > +3: sll.d t3, t3, t1
> > + or t2, t2, t3
> > + addi.d t1, t1, -8
> > + addi.d a0, a0, -1
> > + addi.d a2, a2, -1
> > + bgt a2, zero, 2b
> bgtz
> > +4: st.d t2, a1, 0
> > +
> > + move a0, a2
> > + jr ra
> > +
> > +5: li.w a0, -EFAULT
> > + jr ra
> > +
> > + fixup_ex 1, 6, 1
> > + fixup_ex 2, 6, 0
> > + fixup_ex 4, 6, 0
> > +SYM_FUNC_END(unaligned_read)
> > +
> > +/*
> > + * unsigned long unaligned_write(void *addr, unsigned long value, unsigned long n)
> > + *
> > + * a0: addr
> > + * a1: value
> > + * a2: n
> > + */
> > +SYM_FUNC_START(unaligned_write)
> > + beqz a2, 3f
> > +
> > + li.w t0, 0
> > +1: srl.d t1, a1, t0
> > +2: st.b t1, a0, 0
> > + addi.d t0, t0, 8
> > + addi.d a2, a2, -1
> > + addi.d a0, a0, 1
> > + bgt a2, zero, 1b
> bgtz
OK, thanks.
> > +
> > + move a0, a2
> > + jr ra
> > +
> > +3: li.w a0, -EFAULT
> > + jr ra
> > +
> > + fixup_ex 2, 4, 1
> > +SYM_FUNC_END(unaligned_write)
>
> Thanks,
>
> Jinyang
>
next prev parent reply other threads:[~2022-10-17 7:37 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 [this message]
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
2022-10-17 14:19 ` kernel test robot
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