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linux-next/arch/s390/kvm
Michael Mueller cc674ef252 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>
2020-02-27 19:47:13 +01:00
..
diag.c KVM: s390: protvirt: Report CPU state to Ultravisor 2020-02-27 19:47:12 +01:00
gaccess.c treewide: Use array_size() in vmalloc() 2018-06-12 16:19:22 -07:00
gaccess.h KVM: s390: Remove redundant license text 2017-12-06 09:18:42 +01:00
guestdbg.c KVM: s390: introduce defines for control registers 2018-05-17 09:02:27 +02:00
intercept.c KVM: s390: protvirt: Report CPU state to Ultravisor 2020-02-27 19:47:12 +01:00
interrupt.c KVM: s390: protvirt: Add program exception injection 2020-02-27 19:47:12 +01:00
irq.h KVM: s390: Remove redundant license text 2017-12-06 09:18:42 +01:00
Kconfig * ARM: support for SVE and Pointer Authentication in guests, PMU improvements 2019-05-17 10:33:30 -07:00
kvm-s390.c KVM: s390: introduce module parameter kvm.use_gisa 2020-02-27 19:47:13 +01:00
kvm-s390.h KVM: s390: protvirt: Report CPU state to Ultravisor 2020-02-27 19:47:12 +01:00
Makefile KVM: s390: protvirt: Add initial vm and cpu lifecycle handling 2020-02-27 19:47:11 +01:00
priv.c KVM: s390: protvirt: STSI handling 2020-02-27 19:47:12 +01:00
pv.c KVM: s390: protvirt: Report CPU state to Ultravisor 2020-02-27 19:47:12 +01:00
sigp.c KVM: s390: introduce and use kvm_s390_test_cpuflags() 2018-01-24 17:46:42 +01:00
trace-s390.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
trace.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
vsie.c KVM: s390: vsie: Return correct values for Invalid CRYCB format 2019-04-29 09:01:22 +02:00