[PATCH] kvm: Add documentation for KVM_CAP_NR_VCPUS

[PATCH] kvm: Add documentation for KVM_CAP_NR_VCPUS

[Pekka Enberg]

Document KVM_CAP_NR_VCPUS that can be used by the userspace to determine
maximum number of VCPUs it can create with the KVM_CREATE_VCPU ioctl.

Cc: Avi Kivity <avi@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Jan Kiszka <jan.kiszka@web.de>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
---
 Documentation/kvm/api.txt |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/Documentation/kvm/api.txt b/Documentation/kvm/api.txt
index 9bef4e4..54d603f 100644
--- a/Documentation/kvm/api.txt
+++ b/Documentation/kvm/api.txt
@@ -175,7 +175,8 @@ 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).
+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.
 
 4.8 KVM_GET_DIRTY_LOG (vm ioctl)
 
-- 
1.7.0.4

Re: [PATCH] kvm: Add documentation for KVM_CAP_NR_VCPUS

[Avi Kivity]

On 05/07/2011 05:42 PM, Pekka Enberg wrote:
> Document KVM_CAP_NR_VCPUS that can be used by the userspace to determine
> maximum number of VCPUs it can create with the KVM_CREATE_VCPU ioctl.
>

This capability was added in 2.6.26; so the documentation should state 
that if the capability is not available the user should assume 4 cpus 
max (the limit at the time).

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.