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From: Al Viro <viro@zeniv.linux.org.uk>
To: Guo Ren <guoren@kernel.org>
Cc: Zhenzhong Duan <zhenzhong.duan@gmail.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-csky@vger.kernel.org, Oleg Nesterov <oleg@redhat.com>
Subject: Re: [PATCH] csky: Fix a size determination in gpr_get()
Date: Wed, 23 Sep 2020 05:52:31 +0100	[thread overview]
Message-ID: <20200923045231.GH3421308@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CAJF2gTSU4e4yU63z1q502SeuTf2m2BKaD0yZ0deFj0TkiVupFg@mail.gmail.com>

On Wed, Sep 23, 2020 at 10:37:31AM +0800, Guo Ren wrote:

> > What's going on there?  The mapping is really weird - assuming
> > you had v0..v31 in the first 32 elements of regs->vr[], you
> > end up with
> >
> > v0 v1 v2 v3 v2 v3 v6 v7 v4 v5 v10 v11 v6 v7 v14 v15
> > v8 v9 v18 v19 v10 v11 v22 v23 v12 v13 v26 v27 v14 v15 v30 v31
> >
> > in the beginning of the output.  Assuming it is the intended
> > behaviour, it's probably worth some comments...
> FPU & VDSP use the same regs. 32 FPU regs' width is 64b and 16 VDSP
> regs' width is 128b.
> 
> vr[0], vr[1] = fp[0] & vr[0] vr[1], vr[2], vr[3] = vdsp reg[0]
> ...
> vr[60], vr[61] = fp[15] & vr[60] vr[61], vr[62], vr[63] = vdsp reg[15]
> vr[64], vr[65] = fp[16]
> vr[66], vr[67] = fp[17]
> ...
> vr[94], vr[95] = fp[31]
> 
> Yeah, this is confusing and I'll add a comment later.

Umm...  It would help if you described these 3 layouts:
	1) kernel-side with VDSP
	2) userland (identical to (1)?)
	3) kernel-side without VDSP
Still confused...

PS: my apologies re commit message - I left a note to myself when doing
that series and then forgot about it ;-/

Anyway, which tree should it go through?  In any case, that fix is
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
and I can take it through vfs.git or you guys can pick in csky tree;
up to you.

  reply	other threads:[~2020-09-23  4:52 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-22  9:15 [PATCH] csky: Fix a size determination in gpr_get() Zhenzhong Duan
2020-09-22 16:29 ` Al Viro
2020-09-23  0:03   ` Guo Ren
2020-09-23  0:23     ` Al Viro
2020-09-23  2:37       ` Guo Ren
2020-09-23  4:52         ` Al Viro [this message]
2020-09-25  6:33           ` Guo Ren
2020-12-23  2:31           ` Zhenzhong Duan
2020-12-23 14:57             ` Guo Ren
2020-12-24  2:21               ` Zhenzhong Duan
2020-09-23  2:23   ` Zhenzhong Duan

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