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authorDavid Hildenbrand <dahi@linux.vnet.ibm.com>2014-10-09 16:10:13 +0400
committerChristian Borntraeger <borntraeger@de.ibm.com>2015-01-23 15:25:37 +0300
commit2444b352c3acf54897b0e2803a7c4e66699f9f43 (patch)
tree42490c1860791c4d674fe8c40aaf77c4d0407ab7 /Documentation/virtual/kvm/api.txt
parent9fbd80828cef1b1bba5a293609a021047bb86a7e (diff)
downloadlinux-2444b352c3acf54897b0e2803a7c4e66699f9f43.tar.xz
KVM: s390: forward most SIGP orders to user space
Most SIGP orders are handled partially in kernel and partially in user space. In order to: - Get a correct SIGP SET PREFIX handler that informs user space - Avoid race conditions between concurrently executed SIGP orders - Serialize SIGP orders per VCPU We need to handle all "slow" SIGP orders in user space. The remaining ones to be handled completely in kernel are: - SENSE - SENSE RUNNING - EXTERNAL CALL - EMERGENCY SIGNAL - CONDITIONAL EMERGENCY SIGNAL According to the PoP, they have to be fast. They can be executed without conflicting to the actions of other pending/concurrently executing orders (e.g. STOP vs. START). This patch introduces a new capability that will - when enabled - forward all but the mentioned SIGP orders to user space. The instruction counters in the kernel are still updated. 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>
Diffstat (limited to 'Documentation/virtual/kvm/api.txt')
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diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 3ca6e0e9a769..df19837e94d4 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -3225,3 +3225,23 @@ userspace from doing that.
If the hcall number specified is not one that has an in-kernel
implementation, the KVM_ENABLE_CAP ioctl will fail with an EINVAL
error.
+
+7.2 KVM_CAP_S390_USER_SIGP
+
+Architectures: s390
+Parameters: none
+
+This capability controls which SIGP orders will be handled completely in user
+space. With this capability enabled, all fast orders will be handled completely
+in the kernel:
+- SENSE
+- SENSE RUNNING
+- EXTERNAL CALL
+- EMERGENCY SIGNAL
+- CONDITIONAL EMERGENCY SIGNAL
+
+All other orders will be handled completely in user space.
+
+Only privileged operation exceptions will be checked for in the kernel (or even
+in the hardware prior to interception). If this capability is not enabled, the
+old way of handling SIGP orders is used (partially in kernel and user space).