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| author | Paolo Bonzini <pbonzini@redhat.com> | 2017-08-22 06:50:18 +0200 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2017-09-22 21:07:24 +0200 |
| commit | b855f8d175a0a26c9798cbc5962bb8c0d9538231 (patch) | |
| tree | 06ef9b853e3700eb33aaccd9ffba4c0922baaf42 /docs/pr-manager.rst | |
| parent | 7c9e527659c67d4d7b41d9504f93d2d7ee482488 (diff) | |
| download | qemu-b855f8d175a0a26c9798cbc5962bb8c0d9538231.tar.gz | |
scsi: build qemu-pr-helper
Introduce a privileged helper to run persistent reservation commands.
This lets virtual machines send persistent reservations without using
CAP_SYS_RAWIO or out-of-tree patches. The helper uses Unix permissions
and SCM_RIGHTS to restrict access to processes that can access its socket
and prove that they have an open file descriptor for a raw SCSI device.
The next patch will also correct the usage of persistent reservations
with multipath devices.
It would also be possible to support for Linux's IOC_PR_* ioctls in
the future, to support NVMe devices. For now, however, only SCSI is
supported.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'docs/pr-manager.rst')
| -rw-r--r-- | docs/pr-manager.rst | 33 |
1 files changed, 33 insertions, 0 deletions
diff --git a/docs/pr-manager.rst b/docs/pr-manager.rst index b6089fb57c..7107e59fb8 100644 --- a/docs/pr-manager.rst +++ b/docs/pr-manager.rst @@ -49,3 +49,36 @@ Alternatively, using ``-blockdev``:: -object pr-manager-helper,id=helper0,path=/var/run/qemu-pr-helper.sock -blockdev node-name=hd,driver=raw,file.driver=host_device,file.filename=/dev/sdb,file.pr-manager=helper0 -device scsi-block,drive=hd + +---------------------------------- +Invoking :program:`qemu-pr-helper` +---------------------------------- + +QEMU provides an implementation of the persistent reservation helper, +called :program:`qemu-pr-helper`. The helper should be started as a +system service and supports the following option: + +-d, --daemon run in the background +-q, --quiet decrease verbosity +-f, --pidfile=path PID file when running as a daemon +-k, --socket=path path to the socket +-T, --trace=trace-opts tracing options + +By default, the socket and PID file are placed in the runtime state +directory, for example :file:`/var/run/qemu-pr-helper.sock` and +:file:`/var/run/qemu-pr-helper.pid`. The PID file is not created +unless :option:`-d` is passed too. + +:program:`qemu-pr-helper` can also use the systemd socket activation +protocol. In this case, the systemd socket unit should specify a +Unix stream socket, like this:: + + [Socket] + ListenStream=/var/run/qemu-pr-helper.sock + +After connecting to the socket, :program:`qemu-pr-helper`` can optionally drop +root privileges, except for those capabilities that are needed for +its operation. To do this, add the following options: + +-u, --user=user user to drop privileges to +-g, --group=group group to drop privileges to |