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Date:      Tue, 24 Apr 2012 00:10:26 -0700
From:      Dave Hayes <dave@jetcafe.org>
To:        freebsd-stable@freebsd.org
Subject:   Attempting to boot into ramdisk on 8.3  
Message-ID:  <201204240710.q3O7AQaQ075735@hugeraid.jetcafe.org>

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I have a build process (which worked at release 7.3) that makes a
bootable ISO using a ramdisk image as the boot volume. At release 8 
it panics right after reporting the real memory size with:

 kernel trap 12 with interrupts disabled

 Fatal trap 12: page fault while in kernel mode
 ...
 [thread pid 0 tid 0 ]
 Stopped at       pmap_enter+0x19a:    moveq (%rcx),%r14

(I have the text frozen on another screen if more data is needed, I've
literally spent weeks trying to get this panic to appear on the screen
so it's not going anywhere.)

I build the world with this system without cross compiling. 

# uname -mrs
FreeBSD 8.3-RC1 amd64 

The system that paniced is very similar: a 64-bit amd4 system.

What am I doing wrong, if anything? How can I do a successful large
ramdisk boot? My process is to copy the entire OS to a ramdisk and boot
off of that. I use the following ideas for this:

/boot/loader.conf: 
 mfsroot_type="mfs_root"
 mfsroot_name="/mfsboot"
 vfs.root.mountfrom="ufs:md0"
 vfs.root.mountfrom.options="rw"

 ## Tunables
 kern.ipc.nmbclusters=32768
 net.inet.tcp.tcbhashsize=16384
 vm.pmap.pg_ps_enabled=1
 accf_http_load="YES"
 net.inet.tcp.syncache.hashsize=1024
 net.inet.tcp.syncache.bucketlimit=100

The size of mfsboot is 600M. 

The diff between GENERIC and my kernel config, comments left in
so people can see what I was doing 7.3ish:

 28.43d26
 < ### FBCD64 SPECIFIC
 < #options		MD_ROOT_SIZE="524288"
 < options		GEOM_UZIP
 < #options		INCLUDE_CONFIG_FILE
 < #options		ZERO_COPY_SOCKETS
 < #options		HZ=1000
 < #options		DEVICE_POLLING
 < #options		NKPT=600        # not set up on amd64
 < #
 < # Debugging
 < options		KDB
 < options		DDB
 < options		BREAK_TO_DEBUGGER
 < options		ALT_BREAK_TO_DEBUGGER

Thanks in advance for any assistance!
-- 
Dave Hayes - Consultant - Altadena CA, USA - dave@jetcafe.org 
>>> The opinions expressed above are entirely my own <<<

One of the most common defenses against really learning
something is to believe that one knows it already.







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