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KVM: Update documentation to include detailed ENABLE_CAP description

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We have an ioctl that enables capabilities individually, but no description
on what exactly happens when we enable a capability using this ioctl.

This patch adds documentation for capability enabling in a new section
of the API documentation.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Alexander Graf 2011-08-31 10:58:55 +02:00 committed by Avi Kivity
parent 19ccb76a19
commit 821246a5a5
1 changed files with 47 additions and 0 deletions
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Documentation/virtual/kvm/api.txt
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@ -1653,3 +1653,50 @@ developer registration required to access it).
char padding[256];
};
};
6. Capabilities that can be enabled
There are certain capabilities that change the behavior of the virtual CPU when
enabled. To enable them, please see section 4.37. Below you can find a list of
capabilities and what their effect on the vCPU is when enabling them.
The following information is provided along with the description:
Architectures: which instruction set architectures provide this ioctl.
x86 includes both i386 and x86_64.
Parameters: what parameters are accepted by the capability.
Returns: the return value. General error numbers (EBADF, ENOMEM, EINVAL)
are not detailed, but errors with specific meanings are.
6.1 KVM_CAP_PPC_OSI
Architectures: ppc
Parameters: none
Returns: 0 on success; -1 on error
This capability enables interception of OSI hypercalls that otherwise would
be treated as normal system calls to be injected into the guest. OSI hypercalls
were invented by Mac-on-Linux to have a standardized communication mechanism
between the guest and the host.
When this capability is enabled, KVM_EXIT_OSI can occur.
6.2 KVM_CAP_PPC_PAPR
Architectures: ppc
Parameters: none
Returns: 0 on success; -1 on error
This capability enables interception of PAPR hypercalls. PAPR hypercalls are
done using the hypercall instruction "sc 1".
It also sets the guest privilege level to "supervisor" mode. Usually the guest
runs in "hypervisor" privilege mode with a few missing features.
In addition to the above, it changes the semantics of SDR1. In this mode, the
HTAB address part of SDR1 contains an HVA instead of a GPA, as PAPR keeps the
HTAB invisible to the guest.
When this capability is enabled, KVM_EXIT_PAPR_HCALL can occur.