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| author |   Michael Mueller <mimu@linux.ibm.com> | 2020-02-27 10:10:31 +0100 |
|---|---|---|
| committer |   Christian Borntraeger <borntraeger@de.ibm.com> | 2020-02-27 19:47:13 +0100 |
| commit | cc674ef252f4750bdcea1560ff491081bb960954 (patch) | |
| tree | 8f1735b69f2dd1b8fbd4d535ca5b00b50db8a309 /arch/s390/kvm | |
| parent | KVM: s390: protvirt: Add KVM api documentation (diff) | |
| download | linux-dev-cc674ef252f4750bdcea1560ff491081bb960954.tar.xz linux-dev-cc674ef252f4750bdcea1560ff491081bb960954.zip | |
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>
Diffstat (limited to 'arch/s390/kvm')
| -rw-r--r-- | arch/s390/kvm/kvm-s390.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index f4cd436ba979..6b1842a9feed 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -185,6 +185,11 @@ static u8 halt_poll_max_steal = 10; module_param(halt_poll_max_steal, byte, 0644); MODULE_PARM_DESC(halt_poll_max_steal, "Maximum percentage of steal time to allow polling"); +/* if set to true, the GISA will be initialized and used if available */ +static bool use_gisa = true; +module_param(use_gisa, bool, 0644); +MODULE_PARM_DESC(use_gisa, "Use the GISA if the host supports it."); + /* * For now we handle at most 16 double words as this is what the s390 base * kernel handles and stores in the prefix page. If we ever need to go beyond @@ -2732,7 +2737,8 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) kvm->arch.use_skf = sclp.has_skey; spin_lock_init(&kvm->arch.start_stop_lock); kvm_s390_vsie_init(kvm); - kvm_s390_gisa_init(kvm); + if (use_gisa) + kvm_s390_gisa_init(kvm); KVM_EVENT(3, "vm 0x%pK created by pid %u", kvm, current->pid); return 0; |