kern/87586: Unable to use networked swap in 6.0-RC1

[Greg Lewis]

>Number:         87586
>Category:       kern
>Synopsis:       Unable to use networked swap in 6.0-RC1
>Confidential:   no
>Severity:       serious
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Mon Oct 17 21:10:26 GMT 2005
>Closed-Date:
>Last-Modified:
>Originator:     Greg Lewis
>Release:        FreeBSD 6.0-RC1 sparc64
>Organization:
FreeBSD Project
>Environment:
	FreeBSD 6.0-RC1/sparc64

>Description:

	I tested 6.0-RC1 on my sparc64 machine (Ultra 10) yesterday.
	The machine is set up to boot in a diskless configuration and
	also uses a networked swap file (it only has 128M of RAM).

	As soon as the machine tries to use the swap file it panics.
	The panic message (from memory) was:

	panic: trap: fast mmu data miss

	This is different than the panic message I received with 6.0-BETA1.
	Unfortunately I've not been able to get a trace yet as the
	GENERIC kernel doesn't appear to have KDB etc. in it for RC1.
	I tried to build a kernel with it in, but unfortunately linking
	the kernel requires swap space.
	
	I've also seen this with 6.0-BETA1/alpha, so I don't believe
	this is MD.  The panic message was different however, but that
	may be due to RC1 being compiled without WITNESS etc. compared
	to BETA1.

	Complete details of the original panic with BETA1 were posted
	to freebsd-sparc64 and freebsd-current.  See:

	http://docs.freebsd.org/cgi/getmsg.cgi?fetch=605990+0+archive/2005/freebsd-current/20050724.freebsd-current

	Note that this appears to be a regression from 5.4 which allows
	me to swap to a networked swap file without any problems.

>How-To-Repeat:
	
	Try to use a networked swap file.

>Fix:

	I haven't had the time to investigate a fix.
>Release-Note:
>Audit-Trail:
>Unformatted: