Apparently kernel patch "x86/cpa: Use pte_attrs instead of pte_flags on
CPA/set_p.._wb/wc operations" (in out repo) doesn't fully solve the
problem and sometimes qubes-gui agent crashes with message like
"qubes-gui:664 map pfn expected mapping type write-back for [mem
0x00093000-0x00093fff], got uncached-minus".
Because PAT we really need only in dom0 (lack of it dramatically
decrease performance of some graphics drivers), we can simply disable it
in VM - as it is currently done in upstream kernel.
Apparently it doesn't work with some kernels - saved domain still needs
original memory amount to restore successfully. This happens at least on
3.12.14 kernel.
Because qfile-daemon-dvm always requests 400MB from qmemman, this change
should harm anyone - in any case DispVM needs 400MB free memory to
start.
Note that "xl mem-set" line is still there, which makes savefile somehow
smaller (so faster restore).
If someone really needs it for debuging he/she should be able to either
do it manually (xl network-attach...) or at worst case retrieve this
tool from git history.
This is especially important when kernel-qubes-vm's %post was executed
before qubes-core-dom0's %post - in that case, the default kernel would
be left as "None".
Do not pollute environment of calling process, otherwise all VMs started
from Qubes Manager afterwards will get QREXEC_STARTUP_NOWAIT, which
will cause wait_for_session not working.
Opening a DispVM when the TemplateVM is running forces savefile
regeneration. Checking real root.img modification time (taking into
account root-cow.img) is tricky, so display a warning instead.
When netvm and firewallvm is shut down, netvm handling code will
try to revoke firewallvm access to external IP. But if netvm shutdown
happens in the meantime, xenstore will throw ENOENT error.
The backup_cancel() method kills processes registered by main thread and
set "running_backup_operation.canceled" to True. Then main thread get an
error because of killed processes and check if that was because of
cancel request.
Introduce BackupCanceledError, which can report temporary dir to remove.
Do wait for nest reported filename only when restoring directly from
dom0. In VM case it isn't necessary and will cause false error report
(because filename will be set to nextfile at the end of restore process,
so will be treated as spurious file without hmac).
Simply get device major-minor from /dev/ device file.
This is only partial solution, because this will work only for dom0
devices, but the same problem can apply to VM.
