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KVM: s390: allow user space to handle instr 0x0000

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We will use illegal instruction 0x0000 for handling 2 byte sw breakpoints
from user space. As it can be enabled dynamically via a capability,
let's move setting of ICTL_OPEREXC to the post creation step, so we avoid
any races when enabling that capability just while adding new cpus.

Acked-by: Janosch Frank <frankja@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@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
2016-06-21 14:19:51 +02:00
committed by Christian Borntraeger
parent af1bae5497
commit 6502a34cfd
5 changed files with 43 additions and 2 deletions
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13
Documentation/virtual/kvm/api.txt
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@@ -3857,6 +3857,19 @@ as a broadcast even in x2APIC mode in order to support physical x2APIC
without interrupt remapping. This is undesirable in logical mode,
where 0xff represents CPUs 0-7 in cluster 0.
7.8 KVM_CAP_S390_USER_INSTR0
Architectures: s390
Parameters: none
With this capability enabled, all illegal instructions 0x0000 (2 bytes) will
be intercepted and forwarded to user space. User space can use this
mechanism e.g. to realize 2-byte software breakpoints. The kernel will
not inject an operating exception for these instructions, user space has
to take care of that.
This capability can be enabled dynamically even if VCPUs were already
created and are running.
8. Other capabilities.
----------------------