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authorCarsten Otte <cotte@de.ibm.com>2012-01-04 10:25:26 +0100
committerAvi Kivity <avi@redhat.com>2012-03-05 14:52:20 +0200
commitccc7910fe564d99415def7c041fa261e62a43011 (patch)
tree8895fd2463f7b4e48c4510284c37e84a1753ee0d /Documentation/virtual
parentd6b6d166864fa97ca3b1ed1a5c62fd3b53d4606f (diff)
KVM: s390: ucontrol: interface to inject faults on a vcpu page table
This patch allows the user to fault in pages on a virtual cpus address space for user controlled virtual machines. Typically this is superfluous because userspace can just create a mapping and let the kernel's page fault logic take are of it. There is one exception: SIE won't start if the lowcore is not present. Normally the kernel takes care of this [handle_validity() in arch/s390/kvm/intercept.c] but since the kernel does not handle intercepts for user controlled virtual machines, userspace needs to be able to handle this condition. Signed-off-by: Carsten Otte <cotte@de.ibm.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Avi Kivity <avi@redhat.com>
Diffstat (limited to 'Documentation/virtual')
-rw-r--r--Documentation/virtual/kvm/api.txt16
1 files changed, 16 insertions, 0 deletions
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 5ebf47d99e56..a67fb35993fa 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -1539,6 +1539,22 @@ This ioctl unmaps the memory in the vcpu's address space starting at
"vcpu_addr" with the length "length". The field "user_addr" is ignored.
All parameters need to be alligned by 1 megabyte.
+4.66 KVM_S390_VCPU_FAULT
+
+Capability: KVM_CAP_S390_UCONTROL
+Architectures: s390
+Type: vcpu ioctl
+Parameters: vcpu absolute address (in)
+Returns: 0 in case of success
+
+This call creates a page table entry on the virtual cpu's address space
+(for user controlled virtual machines) or the virtual machine's address
+space (for regular virtual machines). This only works for minor faults,
+thus it's recommended to access subject memory page via the user page
+table upfront. This is useful to handle validity intercepts for user
+controlled virtual machines to fault in the virtual cpu's lowcore pages
+prior to calling the KVM_RUN ioctl.
+
5. The kvm_run structure
Application code obtains a pointer to the kvm_run structure by