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FreeBSD host notes:
- needs to run as root in order to use /dev/tap* networking (why?)
(actually RELENG_6 and above now has a sysctl net.link.tap.user_open
to allow users to use it too. don't forget to adjust device node
permissions in /etc/devfs.rules.)
- slirp (usermode networking) is fixed now in cvs, on FreeSBIE 1.0 guests
you still have to manually do:
echo nameserver 10.0.2.3 >/etc/resolv.conf
but i've been told that that's normal. (fixed on FreeSBIE 1.1.)
and you have to wait a bit for dhclient to do its thing; traffic to
address 10.0.2.2 is routed to 127.1 on the host.
- expect timer problems when guest kernel HZ is > hosts,
for example time sleep 1 takes 49 seconds and booting sleeps for
minutes at the acd0 probe with a FreeSBIE 1.0 guest, thats because
its kernel is built with HZ=5000, and FreeBSD's default is 100...
(no longer a problem with FreeSBIE 1.1.) The linux 2.6 kernel uses
1000 by default btw (changed to 250 recently). Enabling /dev/rtc doesn't
seem to help either (not included since it needs a patch to emulators/rtc.)
- using physical media doesn't work on 4.x hosts (missing DIOCGMEDIASIZE
ioctl.)
- the -smb option (smb-export local dir to guest) needs the net/samba3
port/package installed in addition to qemu.
- RELENG_6 and up guests often crash while accessing the emulated cdrom
(see kern/84102, http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/84102),
using a kernel without PREEMPTION has been reported to fix this problem.
(or do an ftp install instead of installing from the emulated cdrom, and
then make a new kernel.) [fixed since 6.0-R.]
- 6.0-RC1 was released with an ed driver that doesn't like qemu's emulated
RTL8029 nic, this has been fixed in the meantime but if for some reason
you need to use that version as a guest you can temporarily add the patch
in this message: http://docs.freebsd.org/cgi/mid.cgi?200510131428.21211.jkim
(not included in the port since the used VIA VT86C926 PCI ID does not
really match the emulated nic exactly, it just `happens' to work with
6.0-RC1's driver.)
- if you want to use usb devices connected to the host in the guest
(usb_add host:... monitor command; this doesn't work on -current atm
because of the new usb stack - help updating the usb-bsd.c code is
more than welcome here!) you need to make sure the host isn't claiming
them, e.g. for umass devices (like memory sticks or external harddrives)
make sure umass isn't in the kernel (you can then still load it as a kld
when needed), also unless you are running qemu as root you then need to
fix permissions for /dev/ugen* device nodes: if you are on 5.x or later
(devfs) put a rule in /etc/devfs.rules, activate it in /etc/rc.conf
and run /etc/rc.d/devfs restart. example devfs.rules:
[ugen_ruleset=20]
add path 'ugen*' mode 660 group operator
corresponding rc.conf line:
devfs_system_ruleset="ugen_ruleset"
- still usb: since the hub is no longer attached to the uchi controller
and the wakeup mechanism, resume interrupt is not implemented yet linux
guests will suspend the bus, i.e. they wont see devices usb_add'ed after
its (linux') uhci module got loaded. workaround: either add devices
before linux loads the module or rmmod and modprobe it afterwards.
- to avoid panics or non-working re(4) nics with FreeBSD guests if you
use qemu -net nic,model=rtl8139 -net user or tap ... enable the emulated
rtl8139 timer by building the port with RTL8139_TIMER enabled.
(the rtl8139c+ that model=rtl8139 emulates needs less cpu than qemu's
default ne2k nic which is driven by ed(4), it has not been made default
only because it may not work with all guests yet. btw qemu now also can
emulate a few intel eepro100 and e1000 nics which seem to be a tad more
efficient even, and at least i82557b and e1000 work without tweaks for
FreeBSD guests - driven by fxp(4) and em(4) repectively - and Linux
guests too.)
- if you get repeated `atapi_poll called!' console messages with FreeBSD
guests or other weird cdrom problems then thats probably because the guest
has atapicam loaded, which for reasons still to be determined has problems
with qemu's now by default enabled cdrom dma. You can build the port with
CDROM_DMA disabled to disable it.
- if you build qemu wihout SDL and then get crashes running it try
passing it -nographic. This should probably be default in that case...
- slirp (-net user) seems to be unstable on amd64 hosts, if this affects
you please use tuntap for now. Scott Robbins posted a tap howto for
-current here:
http://forums.bsdnexus.com/viewtopic.php?id=1563
and one for 6 and 5(?) is here:
http://acidos.bandwidth-junkies.net/index.php?Sect=qemu
- perhaps it should be noted that if you want to use qemu with -m 512
or larger on 6.x/i386 hosts you need to increase the kern.maxdsiz tunable
in loader.conf(5) since the default is 512 MB, and qemu needs memory for
itself also. (7.0 and up now use jemalloc which uses mmap(2) and
isn't affected by kern.maxdsiz anymore.)
- if you use kqemu make sure your kqemu.ko is always in sync with your
kernel (like with any kld installed outside of base), i.e. rebuild its
port whenever you update the kernel - especially if you are switching
branches or are following a -stable or even -current branch!
- you can enable autoloading of kqemu (and aio) at boot by adding a line
kqemu_enable=YES
to /etc/rc.conf
- kqemu liked to panic the host on amd64 SMP until before 1.3.0.p11_6
(revision 1.25 of /usr/ports/emulators/kqemu-kmod/Makefile), so if your
host is such you might want to make sure your kqemu-kmod port is new enough.
(and don't forget to reload it...)
- qemu's network boot roms (-boot n) have a bug when bootfiles sizes are a
multiple of blksize, if this affects you (like with FreeBSD's /boot/pxeboot)
you can do like
cp /boot/pxeboot pxeboot-qemu && chmod +w pxeboot-qemu && echo >>pxeboot-qemu
and then use pxeboot-qemu. Actually you need latest -stable or -current
btx code (from after 7.0 was released) because of the real mode boot problem,
so use at least pxeboot from there. And I just did that for the pxeboot
extracted out of
ftp://ftp.freebsd.org/pub/FreeBSD/snapshots/200805/7.0-STABLE-200805-i386-bootonly.iso
and placed it here:
http://people.freebsd.org/~nox/qemu/pxeboot-qemu
- if you use slirp (usernet, the default) and want to mount nfs into the
guest and you are not running qemu as root, then mountd(8) on the exporting
box needs to be run with -n in order to accept requests from ports >= 1024.
- unfortunately there can still be guests that don't run correctly with
kqemu and -kernel-kqemu especially on amd64 - not much you can do about that
other than help debugging (k)qemu... (well or falling back to unaccellerated
qemu/leaving out -kernel-kqemu if its that what's causing the problems.
note however that kqemu now can also be used with the 32 bit qemu even
on amd64 hosts as of the 20080620 update.)
- the new (optional) pcap code cannot talk to the host on 6.x because
the necessary bpf feature (BIOCFEEDBACK) hasn't (yet?) been merged there.
- kqemu passes the host tsc to the guest as-is so depending on your cpu and
guest you _may_ need to tell the guest to avoid relying on the tsc (notsc
kernel parameter with linux), or if that doesn't work force qemu onto
a single cpu by doing e.g. `cpuset -l 0 qemu ..' (see the cpuset(1) manpage
for details; cpuset isn't avalable before 7.1. This can only be a problem
on smp hosts.)
- the new sparc64-bsd-user target (qemu-sparc64) is entirely untested and
probably only works on amd64 hosts, if at all.
- (not FreeBSD-specific:) there have been reports of qcow2 corruption with
(at least) win2k guests on recent kvm (which uses similar qcow2 code than
qemu now, see this thread:
http://lists.gnu.org/archive/html/qemu-devel/2009-02/msg00713.html -
the consensus on that thread seems to be that qcow(2) code has always
been experimental and you should use raw images if you want reliability;
raw is also usually faster.) You should be able to migrate existing images
to raw using qemu-img(1)'s convert function; raw doesn't support advanced
features like snapshots tho.
- (also not FreeBSD-specific:) It is recommended to pass raw images using
the new -drive syntax, specifying format=raw explicitly in order to avoid
malicious guests being able to exploit the format autodetection thats
otherwise getting used. (Not that you should run malicious guests anyway,
but this eleminates at least a known attack vector.)
- qemu now uses aio at least for ide dma, so if you get `Invalid system call'
crashes that is because aio is not (kld)loaded.
- The default configuration location (qemu-ifup script etc.) has been
changed from /etc to PREFIX/etc (usually /usr/local/etc). Move your
files accordingly.
- *** This port (qemu-devel) is currently at an older version
(0.9.1s.20080620) than the main port (qemu), so probably should only be
used if there are specific problems with the latter. ***
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