Otherwise deadlock could happen - the script will try to get read lock
on qubes.xml, while the calling tool can already hold the lock. If that
was write lock (which is in case of qfile-daemon-dvm), the deadlock
occurs.
This is the only place where ID was used - all other places uses name.
Linux qrexec-client accepts both ID and name, but sticking to one option
will simplify things (especially Windows qrexec-client/daemon).
None of found existing portable locking module does support RW locks.
Use lowlevel system locking support - both Windows and Linux support
such feature.
Drop locking code in write_firewall_conf() b/c is is called with
QubesVmCollection lock held anyway.
Currently <vm-dir>/<vm-name>.conf file is used only for debugging
purposes - the real one is passed directly to libvirt, without storing
on disk for it.
In some cases (e.g. qvm-clone) QubesVM.create_config_file() can be
called before VM directory exists and in this case it would fail.
Because it isn't critical fail in any means (the config file will be
recreated on next occasion) just ignore this error.
Final version most likely will have this part of code removed
completely.
Mostly done. Things still using xenstore/not working at all:
- DispVM
- qubesutils.py (especially qvm-block and qvm-usb code)
- external IP change notification for ProxyVM (should be done via RPC
service)
libvirt_domain object needs to be recreated, so force it. Also fix
config path setting (missing extension) - create_config_file
uses it as custom config indicator (if such detected, VM settings -
especially name, would not be updated).
This makes easier to import right objects in submodules (only one
object). This also implement lazy connection - at first access, not at
module import, which speeds up tools, which doesn't need runtime
information (like qvm-prefs or qvm-service). In the future this will
ease migration from xenstore to QubesDB.
Also implement "offline mode" - operate on qubes.xml without connecting
to VMM - raise exception at such try.
This is needed to run tools during installation, where only minimal
set of services are started, especially no libvirt.
Do not recreate them at each startup. This will save some time and also
solve some problems from invalidated libvirt handles after domain
shutdown (e.g. causes qubes-manager crashes).
This requires storing uuid in qubes.xml.
Check maxmem taking into account the minimum init memory that allows
that requested maximum memory.
Explanation:
Linux kernel needs space for memory-related structures created at boot.
If init_mem is just 400MB, then max_mem can't balloon above 4.3GB (at
which poing it yields "add_memory() failed: -17" messages and apps
crash), regardless of the max_mem_size value.
Based on Marek's findings and my tests on a 16GB PC, using several
processes like:
stress -m 1 --vm-bytes 1g --vm-hang 100
result in the following points:
init_mem ==> actual max memory
400 4300
700 7554
800 8635
1024 11051
1200 12954
1300 14038
1500 14045 <== probably capped on my 16GB system
The actual ratio of max_mem_size/init_mem is surprisingly constant at
10.79
If less init memory is set than that ratio allows, then the set
maxmem is unreachable and the VM becomes unstable (app crashes)
Based on qubes-devel discussion titled "Qubes Dom0 init memory against
Xen best practices?" at:
https://groups.google.com/d/msg/qubes-devel/VRqkFj1IOtA/UgMgnwfxVSIJ
