Increase dom0 scheduling weight

Dom0 is responsible for the UI and for critical background activities.
In particular, it is on the critical path for VM start.  Therefore, it
should be prioritized over all other VMs to avoid priority inversion.

Dom0 has been intended to have additional credit since
a179894 ("Initial public commit."), but nowadays Xen uses the
credit2 scheduler, so changing the parameters of the credit scheduler
has no effect.

Fixes: QubesOS/qubes-issues#10778
Fixes: a179894 ("Initial public commit.")

Author: DemiMarie

linux/aux-tools/startup-misc.sh

@@ -6,7 +6,7 @@
 DOM0_MAXMEM=$(/usr/sbin/xl list 0 | tail -1 | awk '{ print $3 }')
 xenstore-write /local/domain/0/memory/static-max $[ $DOM0_MAXMEM * 1024 ]
 
-xl sched-credit -d 0 -w 2000
+xl sched-credit2 -d 0 -w 2000
 cp /var/lib/qubes/qubes.xml /var/lib/qubes/backup/qubes-$(date +%F-%T).xml
 
 /usr/lib/qubes/cleanup-dispvms