data corruption with ahc driver and 4GB of memory using a FBSD-8 64-bit installation?

[Gary Jennejohn]

On Thu, 31 Jan 2008 10:51:34 -0700
Scott Long <scottl at samsco.org> wrote:

> Gary Jennejohn wrote:
> > I think $(subject) says it all.
> > 
> > I have a Gigabyte AM2 mobo with an AMD64 X2 CPU installed.
> > 
> > The SCIS set up looks lie this:
> > 
> > 29160N <--> da0 <--> da1
> > 
> > da0 has a 32-bit installation of FBSD-8
> > da1 has a 64-bit installtion of FBSD-8
> > 
> > If I install 4GB of memory (4 DIMMs) in the system I see the following
> > behavior:
> > 
> > a) booting from da0 works just fine and I can access both disks without
> > any problem.
> > 
> > b) booting from da1 results in (apparent) data errors such that /bin/sh
> > dies with SIGILL and /rescue/sh dies with SIGSEGV.
> > 
> > c) trying to do an installation of a snapshot of FBSD-8 to a SCSI disk
> > results in various problems, among others a kernel panic in ffs_balloc
> > during newfs.
> > 
> > d) an installation to a SATA disk succeeds and the system runs just
> > fine.
> > 
> > With only 3GB of memory everything works. Of course, I'd really like to
> > be able to use the entire 4GB. And I want to keep my SCSI disks.
> > 
> > I suspect that ahc has some sort of problem in 64-bit mode. However,
> > I'm not certain whether the 32-bit installation works with 4GB simply
> > because the ahc driver uses bounce buffers.
> > 
> > Has anybody else seen this? Can anyone confirm that ahc does indeed
> > have an error with 4GB and a 64-bit installation?
> > 
> > BTW please put me in the Cc because I'm not subscribed to this ML.
> > 
> 
> The ahc driver should work with >4GB, and in fact that was a standard
> part of the test suite back when it was still in active development.  If
> it doesn't work now then it's due to some sort of bitrot.  I can try to
> test and debug it myself, but I'm pretty overcommitted so I can't
> guarantee that I'll get to it.  If others would like to help test and
> debug, I'm happy to answer questions and provide assistance.
> 

Well, the thing which I find confusing is that the 32-bit installation
works without any problems.  I would expect the 64-bit installation to
work with 4GB, if anything does.

Does the 32-bit version use bounce buffers?

I'll try poking around some, but the 64-bit install is my (money earning)
work station and I can't afford to trash it, so I'm sort of unwilling to
risk it.  And I don't have any spare SCSI disks to use for testing.  Well,
I suppose I could sacrifice the 32-bit disk.  It's not so important.

Any hints on where to start looking?

---
Gary Jennejohn