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-rw-r--r--Documentation/virtual/kvm/api.txt11
1 files changed, 9 insertions, 2 deletions
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index b0e4b9cd6a66..75cd8fba0cde 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -175,10 +175,17 @@ Parameters: vcpu id (apic id on x86)
Returns: vcpu fd on success, -1 on error
This API adds a vcpu to a virtual machine. The vcpu id is a small integer
-in the range [0, max_vcpus). You can use KVM_CAP_NR_VCPUS of the
-KVM_CHECK_EXTENSION ioctl() to determine the value for max_vcpus at run-time.
+in the range [0, max_vcpus).
+
+The recommended max_vcpus value can be retrieved using the KVM_CAP_NR_VCPUS of
+the KVM_CHECK_EXTENSION ioctl() at run-time.
+The maximum possible value for max_vcpus can be retrieved using the
+KVM_CAP_MAX_VCPUS of the KVM_CHECK_EXTENSION ioctl() at run-time.
+
If the KVM_CAP_NR_VCPUS does not exist, you should assume that max_vcpus is 4
cpus max.
+If the KVM_CAP_MAX_VCPUS does not exist, you should assume that max_vcpus is
+same as the value returned from KVM_CAP_NR_VCPUS.
On powerpc using book3s_hv mode, the vcpus are mapped onto virtual
threads in one or more virtual CPU cores. (This is because the
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