KVM: s390: Features and Enhancements for 5.7 part1
1. Allow to disable gisa
2. protected virtual machines
Protected VMs (PVM) are KVM VMs, where KVM can't access the VM's
state like guest memory and guest registers anymore. Instead the
PVMs are mostly managed by a new entity called Ultravisor (UV),
which provides an API, so KVM and the PV can request management
actions.
PVMs are encrypted at rest and protected from hypervisor access
while running. They switch from a normal operation into protected
mode, so we can still use the standard boot process to load a
encrypted blob and then move it into protected mode.
Rebooting is only possible by passing through the unprotected/normal
mode and switching to protected again.
One mm related patch will go via Andrews mm tree ( mm/gup/writeback:
add callbacks for inaccessible pages)
KVM: s390: introduce module parameter kvm.use_gisa
The boolean module parameter "kvm.use_gisa" controls if newly
created guests will use the GISA facility if provided by the
host system. The default is yes.
# cat /sys/module/kvm/parameters/use_gisa
Y
The parameter can be changed on the fly.
# echo N > /sys/module/kvm/parameters/use_gisa
Already running guests are not affected by this change.
The kvm s390 debug feature shows if a guest is running with GISA.
# grep gisa /sys/kernel/debug/s390dbf/kvm-$pid/sprintf
00 01582725059:843303 3 - 08 00000000e119bc01 gisa 0x00000000c9ac2642 initialized
00 01582725059:903840 3 - 11 000000004391ee22 00[0000000000000000-0000000000000000]: AIV gisa format-1 enabled for cpu 000
...
00 01582725059:916847 3 - 08 0000000094fff572 gisa 0x00000000c9ac2642 cleared
In general, that value should not be changed as the GISA facility
enhances interruption delivery performance.
A reason to switch the GISA facility off might be a performance
comparison run or debugging.
Signed-off-by: Michael Mueller <mimu@linux.ibm.com>
Link: https://lore.kernel.org/r/20200227091031.102993-1-mimu@linux.ibm.com
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
1 file changed
