From: Greg KH <greg@kroah.com>
To: "Maciej W. Rozycki" <macro@linux-mips.org>
Cc: stable@vger.kernel.org, Ralf Baechle <ralf@linux-mips.org>,
Paul Burton <paul.burton@mips.com>
Subject: Re: [PATCH 4.18] MIPS: memset: Fix CPU_DADDI_WORKAROUNDS `small_fixup' regression
Date: Sat, 10 Nov 2018 18:00:08 -0800 [thread overview]
Message-ID: <20181111020008.GD18060@kroah.com> (raw)
In-Reply-To: <alpine.LFD.2.21.1810162222590.16498@eddie.linux-mips.org>
On Tue, Oct 16, 2018 at 10:51:10PM +0100, Maciej W. Rozycki wrote:
> Fix a commit 8a8158c85e1e ("MIPS: memset.S: EVA & fault support for
> small_memset") regression and remove assembly warnings:
>
> arch/mips/lib/memset.S: Assembler messages:
> arch/mips/lib/memset.S:243: Warning: Macro instruction expanded into multiple instructions in a branch delay slot
>
> triggering with the CPU_DADDI_WORKAROUNDS option set and this code:
>
> PTR_SUBU a2, t1, a0
> jr ra
> PTR_ADDIU a2, 1
>
> This is because with that option in place the DADDIU instruction, which
> the PTR_ADDIU CPP macro expands to, becomes a GAS macro, which in turn
> expands to an LI/DADDU (or actually ADDIU/DADDU) sequence:
>
> 13c: 01a4302f dsubu a2,t1,a0
> 140: 03e00008 jr ra
> 144: 24010001 li at,1
> 148: 00c1302d daddu a2,a2,at
> ...
>
> Correct this by switching off the `noreorder' assembly mode and letting
> GAS schedule this jump's delay slot, as there is nothing special about
> it that would require manual scheduling. With this change in place
> correct code is produced:
>
> 13c: 01a4302f dsubu a2,t1,a0
> 140: 24010001 li at,1
> 144: 03e00008 jr ra
> 148: 00c1302d daddu a2,a2,at
> ...
>
> Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
> Fixes: 8a8158c85e1e ("MIPS: memset.S: EVA & fault support for small_memset")
> Cc: stable@vger.kernel.org # 4.17+
> ---
> Hi,
>
> This is a version (one I originally made actually) of commit 148b9aba99e0
> for 4.18-stable and before. No functional changes. Please apply.
Now queued up, thanks.
greg k-h
prev parent reply other threads:[~2018-11-11 13:14 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-16 21:51 [PATCH 4.18] MIPS: memset: Fix CPU_DADDI_WORKAROUNDS `small_fixup' regression Maciej W. Rozycki
2018-11-11 2:00 ` Greg KH [this message]
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