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KVM: s390: forward ESOP if available

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ESOP guarantees that during a protection exception, bit 61 of real location
168-175 will only be set to 1 if it was because of ALCP or DATP. If the
exception is due to LAP or KCP, the bit will always be set to 0.

The old SOP definition allowed bit 61 to be unpredictable in case of LAP
or KCP in some conditions. So ESOP replaces this unpredictability by
a guarantee.

Therefore, we can directly forward ESOP if it is available on our machine.
We don't have to do anything when ESOP is disabled - the guest will simply
expect unpredictable values. Our guest access functions are already
handling ESOP properly.

Please note that future functionality in KVM will require knowledge about
ESOP being enabled for a guest or not.

Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
This commit is contained in:
David Hildenbrand
2016-01-21 13:22:54 +01:00
committed by Christian Borntraeger
parent 15c9705f0c
commit 22be5a1331
2 changed files with 14 additions and 0 deletions
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arch/s390/include/uapi/asm/kvm.h
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@@ -97,6 +97,7 @@ struct kvm_s390_vm_cpu_machine {
#define KVM_S390_VM_CPU_MACHINE_FEAT 3
#define KVM_S390_VM_CPU_FEAT_NR_BITS 1024
#define KVM_S390_VM_CPU_FEAT_ESOP 0
struct kvm_s390_vm_cpu_feat {
__u64 feat[16];
};