From owner-freebsd-current  Mon Mar 19 17:15:55 2001
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Date: Tue, 20 Mar 2001 12:14:00 +1100 (EST)
From: Bruce Evans <bde@zeta.org.au>
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To: John Baldwin <jhb@FreeBSD.ORG>
Cc: Dag-Erling Smorgrav <des@ofug.org>, current@FreeBSD.ORG
Subject: RE: Here's another one for you...
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On Tue, 20 Mar 2001, Bruce Evans wrote:

> On Mon, 19 Mar 2001, John Baldwin wrote:
> 
> > Hmmm.  An eip of 0 is bad.  This could be just another instance of the bzero
> > bug just in another place.  You probably want to change the code that actually
> > sets *bzero to i586_bzero (and same for any other ops that use floating point).
> > The code in question for this lies in i386/isa/npx.c.  It seems we use the fp
> > regs for copyin/copyout and bcopy as well.  I would just change line 458 of
> > npx.c to say '#ifdef I586_CPU_XXX' for now as your temporary patch (then you
> > don't need to patch pmap_zero_page() anymore.)
> 
> There is no need to change anything.  Just disable the fp optimizations
> using the npx flags.

Actually, there may be.  The bandwidth test gets run on 586's even if
the flags say not to use the result.  This is to provide a "free"
bandwidth test.  It was harmless when the fp code wasn't broken.  The
flags are mainly for disabling using the fp code for accesses to broken
device memory (bcopy and/or bzero were (are?) abuses to access device
memory, and some device memory doesn't like 64-bit accesses).

Bruce


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