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+% Hypervisor FS
+% Revision 1
+
+\clearpage
+
+# Basics
+---------------- ---------------------
+ Status: e.g. **Supported**
+
+ Architectures: all
+
+ Components: Hypervisor, toolstack
+---------------- ---------------------
+
+# Overview
+
+The Hypervisor FS is a hierarchical name-value store for reporting
+information to guests, especially dom0. It is similar to the Linux
+kernel's sysfs, but without the functionality to directly alter
+entries values. Entries and directories are created by the hypervisor,
+while the toolstack is able to use a hypercall to query the entry
+values.
+
+# User details
+
+With:
+
+ xenfs --ls <path>
+
+the user can list the entries of a specific path of the FS. Using:
+
+ xenfs --cat <path>
+
+the content of an entry can be retrieved.
+
+The FS structure is:
+
+ /
+ buildinfo/ directory containing build-time data
+ config contents of .config file used to build Xen
+ cpu-bugs/ x86: directory of cpu bug information
+ l1tf "Vulnerable" or "Not vulnerable"
+ mds "Vulnerable" or "Not vulnerable"
+ meltdown "Vulnerable" or "Not vulnerable"
+ spec-store-bypass "Vulnerable" or "Not vulnerable"
+ spectre-v1 "Vulnerable" or "Not vulnerable"
+ spectre-v2 "Vulnerable" or "Not vulnerable"
+ mitigations/ directory of mitigation settings
+ bti-thunk "N/A", "RETPOLINE", "LFENCE" or "JMP"
+ spec-ctrl "No", "IBRS+" or IBRS-"
+ ibpb "No" or "Yes"
+ l1d-flush "No" or "Yes"
+ md-clear "No" or "VERW"
+ l1tf-barrier "No" or "Yes"
+ active-hvm/ directory for mitigations active in hvm doamins
+ msr-spec-ctrl "No" or "Yes"
+ rsb "No" or "Yes"
+ eager-fpu "No" or "Yes"
+ md-clear "No" or "Yes"
+ active-pv/ directory for mitigations active in pv doamins
+ msr-spec-ctrl "No" or "Yes"
+ rsb "No" or "Yes"
+ eager-fpu "No" or "Yes"
+ md-clear "No" or "Yes"
+ xpti "No" or list of "dom0", "domU", "PCID on"
+ l1tf-shadow "No" or list of "dom0", "domU"
+ parameters/ directory with hypervisor parameter values
+ (boot/runtime parameters)
+
+# Technical details
+
+Access to the hypervisor filesystem is done via the stable new hypercall
+__HYPERVISOR_filesystem_op.
+
+* hypercall interface specification
+ * `xen/include/public/filesystem.h`
+* hypervisor internal files
+ * `xen/include/xen/filesystem.h`
+ * `xen/common/filesystem.c`
+* `libxenfs`
+ * `tools/libs/libxenfs/*`
+* `xenfs`
+ * `tools/misc/xenfs.c`
+
+# Testing
+
+Any new parameters or hardware mitigations should be verified to show up
+correctly in the filesystem.
+
+# Areas for improvement
+
+* More detailed access rights
+* Entries per domain and/or per cpupool
+* Possibility to modify values via filesystem access
+
+# Known issues
+
+* None
+
+# References
+
+* None
+
+# History
+
+------------------------------------------------------------------------
+Date Revision Version Notes
+---------- -------- -------- -------------------------------------------
+2019-08-29 1 Xen 4.13 Document written
+---------- -------- -------- -------------------------------------------
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> --- docs/features/hypervisorfs.pandoc | 110 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 110 insertions(+) create mode 100644 docs/features/hypervisorfs.pandoc