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RE: [Xen-devel] FreeBSD boot loader problem on VT-x

Please find my experience with booting FreeBSD on xen-unstable-hvm.hg

Without Anthony's updates, I was able compile and boot xen. However,
FreeBSD 6.1 HVM stalled and didn't boot successfully. Please find the
qemu-dm.log for the session below. Xm list show the domain with no

Domain-0                                   0     1933     8 r-----
FreeBSD                                    3     1024     1 ------

With Anthony's updates, I was not able to compile successfully. I guess
it is a work in progress. I will be happy to try it again once the
latest xen-unstable is merged with HVM code.


domid: 2
qemu: the number of cpus is 1
shared page at pfn:3ffff, mfn: 71400
buffered io page at pfn:3fffd, mfn: 71402
char device redirected to /dev/pts/1
Partition has PAE enabled
False I/O request ... in-service already: 0, pvalid: 0, port: 0, data:
0, count: 0, size: 0
HVM Loader
Detected Xen v3.0-unstable
Writing SMBIOS tables ...
Loading ROMBIOS ...
Loading Cirrus VGABIOS ...
Loading ACPI ...
VMX go ...
rax 0x0000000000000000, rbx 0x0000000000000000, rcx 0x0000000000000000
rdx 0x0000000000000000, rsi 0x0000000000000000, rdi 0x0000000000000000
rbp 0x0000000000000000, rsp 0x0000000000000000, rip 0x000000000000fff0
r8 0x0000000000000000, r9 0x0000000000000000, r10 0x0000000000000000
r11 0x0000000000000000, r12 0x0000000000000000, r13 0x0000000000000000
r14 0x0000000000000000, r15 0x0000000000000000
rflags 0x0000000000000002
Control registers:
cr0 0x60000010, cr2 0x00000000, cr3 0x00000000, cr4 0x00000000
cs: 0xf000, base 0xf0000, limit 0xffff, arbytes 0x89b
ds: 0x0, base 0x0, limit 0xffff, arbytes 0x893
es: 0x0, base 0x0, limit 0xffff, arbytes 0x893
ss: 0x0, base 0x0, limit 0xffff, arbytes 0x893
fs: 0x0, base 0x0, limit 0xffff, arbytes 0x893
gs: 0x0, base 0x0, limit 0xffff, arbytes 0x893
idt: base 0x0, limit 0x3ff
gdt: base 0x0, limit 0x3ff
ldtr: 0x0, base 0x0, limit 0x3ff, arbytes 0x82
tr: 0x0, base 0x0, limit 0x0, arbytes 0x0
EAX=00000000 EBX=00000000 ECX=00000000 EDX=00000000
ESI=00000000 EDI=00000000 EBP=00000000 ESP=00000000
EIP=0000fff0 EFL=00000002 [-------] CPL=0 II=0 A20=1 HLT=0
ES =0000 00000000 0000ffff 00009300
CS =f000 000f0000 0000ffff 00009b00
SS =0000 00000000 0000ffff 00009300
DS =0000 00000000 0000ffff 00009300
FS =0000 00000000 0000ffff 00009300
GS =0000 00000000 0000ffff 00009300
LDT=0000 00000000 000003ff 00008200
TR =0000 00000000 00000000 00000000
GDT=     00000000 000003ff
IDT=     00000000 000003ff

-----Original Message-----
From: M.A. Williamson [mailto:maw48@xxxxxxxxxxxxxxxx] On Behalf Of M.A.
Sent: Wednesday, December 27, 2006 6:29 PM
To: Sanjeepan, Vivekananthan
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx; khoa@xxxxxxx
Subject: Re: [Xen-devel] FreeBSD boot loader problem on VT-x


>I tried unsuccessfully to boot FreeBSD HVM on VT-x hardware. Reading a
>couple of discussion on xen-devel list, I found that other people also
>have the same problem. The problem is identified with real mode
>emulation in VMXAssist.
>In May 2006, one post mentioned plans to replace VMX assist with full
>l). I would like to know if there is a way to get the full emulation
>feature if available. If not, is there an alternative way to boot
>FreeBSD on VT-x.

Information about this project is described here:

Basically, it adds support for extracting CPU state from Xen and putting
into the Qemu CPU emulator and running fully emulated within the device 
model (currently in dom0) for a bit. The state is pushed back into Xen
emulation is no longer necessary and execution continues as normal.

The wiki page includes an address for the repository. It's working for 
booting Linux guests but for other OSes YMMV. If you do test this with 
FreeBSD, could you please let us know how it goes / update the wiki
I'm sure extra data points would be interesting to some.


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