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Juergen Gross
1e9f929b78
Document the interface between qemu and libxl regarding backends supported by qemu. Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com> Reviewed-by: Wei Liu <wei.liu2@citrix.com> Release-acked-by: Wei Liu <wei.liu2@citrix.com>
22 lines
1012 B
Plaintext
22 lines
1012 B
Plaintext
In order to know whether qemu supports a specific backend type libxl
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needs a way to obtain this information.
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As each qemu instance owns a path (named $QEMU from now on) in
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Xenstore, the backend information is presented there. $QEMU is built
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from the domain id where the qemu instance is running $BACKEND_DOM,
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and the domain id of the target domain of the qemu process $DOMID:
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$QEMU = /local/domain/$BACKEND_DOM/device-model/$DOMID
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Before signalling qemu is running by writing "running" to $QEMU/state
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qemu will create a Xenstore node for each supported backend under
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$QEMU/backends with the backend type as name (e.g. $QEMU/backends/qdisk
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for the qdisk backend). In case qemu is running de-privileged (not as
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user root) the backend nodes must be written before qemu is dropping
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privileges.
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libxl can assume a backend of a specific type $TYPE is supported if:
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- $QEMU/backends/$TYPE is existing in Xenstore
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- or $QEMU/backends is not existing and $TYPE is one of:
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"console", "vkbd", "vfb", "qdisk", "qnic"
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