linux-kernel - Re: [PATCH 1/2] MIPS: math-emu: Update debugfs FP exception stats for certain instructions

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Date:   Thu, 12 Oct 2017 17:33:30 +0100
From:   James Hogan <james.hogan@...s.com>
To:     Aleksandar Markovic <Aleksandar.Markovic@...tec.com>
CC:     Aleksandar Markovic <Aleksandar.Markovic@...rk.com>,
        Miodrag Dinic <Miodrag.Dinic@...tec.com>,
        Paul Burton <Paul.Burton@...tec.com>,
        "Petar Jovanovic" <Petar.Jovanovic@...tec.com>,
        Raghu Gandham <Raghu.Gandham@...tec.com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        "linux-mips@...ux-mips.org" <linux-mips@...ux-mips.org>,
        Douglas Leung <Douglas.Leung@...tec.com>,
        Goran Ferenc <Goran.Ferenc@...tec.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Maciej Rozycki <Maciej.Rozycki@...tec.com>,
        Manuel Lauss <manuel.lauss@...il.com>,
        "Masahiro Yamada" <yamada.masahiro@...ionext.com>
Subject: Re: [PATCH 1/2] MIPS: math-emu: Update debugfs FP exception stats
 for certain instructions

On Thu, Oct 12, 2017 at 03:54:48PM +0000, Aleksandar Markovic wrote:
> > This patch fixes something, I think it should
> > a) be clear in the commit message what is fixed
> > b) be tagged for stable (though that can always be done
> > retrospectively)
> 
> If you agree, I am going to submit v2 of the series, that would fully
> address these concerns.
> 
> Additionally, it seems to me that a new round of testing that tests
> involved code paths under various scenarios would be appropriate
> and I am going to do that.

awesome, thanks!

> > Note: thats the one in fpux_emu(), not fpu_emu() which this patch
> > modifies.
> 
> Yes, my bad, wanting to respond as quickly as possible, I inserted
> the segment from fpux_emu(), not fpu_emu() as I should have.
> 
> By the way, and not related to this patch, I see only 4 (out of 5)
> exceptions are handled in fpux_emu() case (division-by-zero is not
> handled), I presume this is fine (probably division-by-zero not
> needed), isn't it?

Yeh I just spotted that too.

I agree that it only seems to be division instructions (fdiv_op,
frsqrt_op, and frecip_op) that need it, which are all handled in
fpu_emu(), so it should be fine as is.

> 
> I truly appreciate your analysis and help.

No problem

Cheers
James