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Juergen Gross
0e9dcd0159
On the 2019 Xen developer summit there was agreement that the Xen hypervisor should gain support for a hierarchical name-value store similar to the Linux kernel's sysfs. In the beginning there should only be basic support: entries can be added from the hypervisor itself only, there is a simple hypercall interface to read the data. Add a feature document for setting the base of a discussion regarding the desired functionality and the entries to add. Signed-off-by: Juergen Gross <jgross@suse.com> Acked-by: Julien Grall <jgrall@amazon.com>
93 lines
2.3 KiB
Plaintext
93 lines
2.3 KiB
Plaintext
% Hypervisor FS
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% Revision 1
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\clearpage
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# Basics
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---------------- ---------------------
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Status: **Supported**
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Architectures: all
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Components: Hypervisor, toolstack
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---------------- ---------------------
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# Overview
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The Hypervisor FS is a hierarchical name-value store for reporting
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information to guests, especially dom0. It is similar to the Linux
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kernel's sysfs. Entries and directories are created by the hypervisor,
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while the toolstack is able to use a hypercall to query the entry
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values or (if allowed by the hypervisor) to modify them.
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# User details
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With:
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xenhypfs ls <path>
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the user can list the entries of a specific path of the FS. Using:
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xenhypfs cat <path>
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the content of an entry can be retrieved. Using:
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xenhypfs write <path> <string>
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a writable entry can be modified. With:
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xenhypfs tree
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the complete Hypervisor FS entry tree can be printed.
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The FS paths are documented in `docs/misc/hypfs-paths.pandoc`.
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# Technical details
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Access to the hypervisor filesystem is done via the stable new hypercall
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__HYPERVISOR_filesystem_op. This hypercall supports a sub-command
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XEN_HYPFS_OP_get_version which will return the highest version of the
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interface supported by the hypervisor. Additions to the interface need
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to bump the interface version. The hypervisor is required to support the
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previous interface versions, too (this implies that additions will always
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require new sub-commands in order to allow the hypervisor to decide which
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version of the interface to use).
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* hypercall interface specification
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* `xen/include/public/hypfs.h`
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* hypervisor internal files
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* `xen/include/xen/hypfs.h`
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* `xen/common/hypfs.c`
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* `libxenhypfs`
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* `tools/libs/libxenhypfs/*`
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* `xenhypfs`
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* `tools/misc/xenhypfs.c`
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* path documentation
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* `docs/misc/hypfs-paths.pandoc`
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# Testing
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Any new parameters or hardware mitigations should be verified to show up
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correctly in the filesystem.
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# Areas for improvement
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* More detailed access rights
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* Entries per domain and/or per cpupool
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# Known issues
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* None
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# References
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* None
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# History
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------------------------------------------------------------------------
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Date Revision Version Notes
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---------- -------- -------- -------------------------------------------
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2020-01-23 1 Xen 4.14 Document written
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---------- -------- -------- -------------------------------------------
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