From: David Daney <ddaney@caviumnetworks.com>
To: Muthu Kumaran <muthukumaranbe@gmail.com>
Cc: linux-mips@linux-mips.org
Subject: Re: Switch FPU emulator trap to BREAK instruction
Date: Fri, 05 Feb 2010 09:36:20 -0800 [thread overview]
Message-ID: <4B6C5714.3080603@caviumnetworks.com> (raw)
In-Reply-To: <4101f55c1002050005t1d7e1b09qe988e39932dfc411@mail.gmail.com>
Muthu Kumaran wrote:
> I am using 2.6.18 linux version on MIPS32 core. One of the application
> is using intensive floating point operations. This hardware doesn't
> have FPU and also the application is not compiled for software
> floating point support.
> Hence, it is using the floating point emulation.
>
> While running that application, On a timer interrupt there is a normal
> integer div instruction which gives wrong result in the HI register.
>
> However, when I applied the following patch, this problem disappeared.
>
> http://kerneltrap.org/mailarchive/git-commits-head/2008/10/30/3873324
>
> When I looked into the patch, handling of invalid instruction
> exception is moved from trap to break.
Incorrect analysis. It was changed from an Adress Error (ADE) exception
to a BREAK.
> There is no other behavioural change in this patch. I really don't
> understand the need for this patch, May I ask someone to explain the
> background information behind this patch? Is this for any known issue?
>
The change log states the reason. FPU emulator delay slot emulation was
failing on some systems.
David Daney
next prev parent reply other threads:[~2010-02-05 17:37 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-02-05 8:05 Switch FPU emulator trap to BREAK instruction Muthu Kumaran
2010-02-05 17:36 ` David Daney [this message]
2010-02-05 20:29 ` Muthu Kumaran
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