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Diffstat (limited to 'docs/about/deprecated.rst')
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diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst index 0743459862..ddc1e48460 100644 --- a/docs/about/deprecated.rst +++ b/docs/about/deprecated.rst @@ -343,6 +343,29 @@ the addition of volatile memory support, it is now necessary to distinguish between persistent and volatile memory backends. As such, memdev is deprecated in favor of persistent-memdev. +``-fsdev proxy`` and ``-virtfs proxy`` (since 8.1) +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +The 9p ``proxy`` filesystem backend driver has been deprecated and will be +removed (along with its proxy helper daemon) in a future version of QEMU. Please +use ``-fsdev local`` or ``-virtfs local`` for using the 9p ``local`` filesystem +backend, or alternatively consider deploying virtiofsd instead. + +The 9p ``proxy`` backend was originally developed as an alternative to the 9p +``local`` backend. The idea was to enhance security by dispatching actual low +level filesystem operations from 9p server (QEMU process) over to a separate +process (the virtfs-proxy-helper binary). However this alternative never gained +momentum. The proxy backend is much slower than the local backend, hasn't seen +any development in years, and showed to be less secure, especially due to the +fact that its helper daemon must be run as root, whereas with the local backend +QEMU is typically run as unprivileged user and allows to tighten behaviour by +mapping permissions et al by using its 'mapped' security model option. + +Nowadays it would make sense to reimplement the ``proxy`` backend by using +QEMU's ``vhost`` feature, which would eliminate the high latency costs under +which the 9p ``proxy`` backend currently suffers. However as of to date nobody +has indicated plans for such kind of reimplemention unfortunately. + Block device options '''''''''''''''''''' |