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https://github.com/xen-project/xen.git
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Juergen Gross
a659d7cab9
Add support to read and modify values of hypervisor runtime parameters via the hypervisor file system. As runtime parameters can be modified via a sysctl, too, this path has to take the hypfs rw_lock as writer. For custom runtime parameters the connection between the parameter value and the file system is done via an init function which will set the initial value (if needed) and the leaf properties. Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Jan Beulich <jbeulich@suse.com> Acked-by: Julien Grall <jgrall@amazon.com>
166 lines
5.4 KiB
Plaintext
166 lines
5.4 KiB
Plaintext
# Xenhypfs Paths
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This document attempts to define all the paths which are available
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in the Xen hypervisor file system (hypfs).
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The hypervisor file system can be accessed via the xenhypfs tool.
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## Notation
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The hypervisor file system is similar to the Linux kernel's sysfs.
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In this document directories are always specified with a trailing "/".
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The following notation conventions apply:
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DIRECTORY/
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PATH = VALUES [TAGS]
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The first syntax defines a directory. It normally contains related
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entries and the general scope of the directory is described.
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The second syntax defines a file entry containing values which are
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either set by the hypervisor or, if the file is writable, can be set
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by the user.
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PATH can contain simple regex constructs following the Perl compatible
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regexp syntax described in pcre(3) or perlre(1).
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A hypervisor file system entry name can be any 0-delimited byte string
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not containing any '/' character. The names "." and ".." are reserved
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for file system internal use.
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VALUES are strings and can take the following forms (note that this represents
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only the syntax used in this document):
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* STRING -- an arbitrary 0-delimited byte string.
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* INTEGER -- An integer, in decimal representation unless otherwise
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noted.
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* "a literal string" -- literal strings are contained within quotes.
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* (VALUE | VALUE | ... ) -- a set of alternatives. Alternatives are
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separated by a "|" and all the alternatives are enclosed in "(" and
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")".
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* {VALUE, VALUE, ... } -- a list of possible values separated by "," and
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enclosed in "{" and "}".
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Additional TAGS may follow as a comma separated set of the following
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tags enclosed in square brackets.
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* w -- Path is writable by the user. This capability is usually
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limited to the control domain (e.g. dom0).
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* ARM | ARM32 | ARM64 | X86: the path is available for the respective
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architecture only.
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* PV -- Path is valid for PV capable hypervisors only.
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* HVM -- Path is valid for HVM capable hypervisors only.
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* CONFIG_* -- Path is valid only in case the hypervisor was built with
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the respective config option.
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So an entry could look like this:
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/cpu-bugs/active-pv/xpti = ("No"|{"dom0", "domU", "PCID-on"}) [w,X86,PV]
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Possible values would be "No" or a list of "dom0", "domU", and "PCID-on" with
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the list elements separated by spaces, e.g. "dom0 PCID-on".
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The entry would be writable and it would exist on X86 only and only if the
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hypervisor is configured to support PV guests.
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## Example
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A populated Xen hypervisor file system might look like the following example:
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/
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buildinfo/ directory containing build-time data
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config contents of .config file used to build Xen
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cpu-bugs/ x86: directory of cpu bug information
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l1tf "Vulnerable" or "Not vulnerable"
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mds "Vulnerable" or "Not vulnerable"
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meltdown "Vulnerable" or "Not vulnerable"
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spec-store-bypass "Vulnerable" or "Not vulnerable"
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spectre-v1 "Vulnerable" or "Not vulnerable"
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spectre-v2 "Vulnerable" or "Not vulnerable"
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mitigations/ directory of mitigation settings
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bti-thunk "N/A", "RETPOLINE", "LFENCE" or "JMP"
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spec-ctrl "No", "IBRS+" or "IBRS-"
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ibpb "No" or "Yes"
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l1d-flush "No" or "Yes"
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md-clear "No" or "VERW"
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l1tf-barrier "No" or "Yes"
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active-hvm/ directory for mitigations active in hvm doamins
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msr-spec-ctrl "No" or "Yes"
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rsb "No" or "Yes"
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eager-fpu "No" or "Yes"
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md-clear "No" or "Yes"
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active-pv/ directory for mitigations active in pv doamins
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msr-spec-ctrl "No" or "Yes"
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rsb "No" or "Yes"
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eager-fpu "No" or "Yes"
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md-clear "No" or "Yes"
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xpti "No" or list of "dom0", "domU", "PCID-on"
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l1tf-shadow "No" or list of "dom0", "domU"
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params/ directory with hypervisor parameter values
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(boot/runtime parameters)
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## General Paths
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#### /
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The root of the hypervisor file system.
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#### /buildinfo/
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A directory containing static information generated while building the
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hypervisor.
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#### /buildinfo/changeset = STRING
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Git commit of the hypervisor.
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#### /buildinfo/compileinfo/
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A directory containing information about compilation of Xen.
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#### /buildinfo/compileinfo/compile_by = STRING
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Information who compiled the hypervisor.
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#### /buildinfo/compileinfo/compile_date = STRING
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Date of the hypervisor compilation.
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#### /buildinfo/compileinfo/compile_domain = STRING
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Information about the compile domain.
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#### /buildinfo/compileinfo/compiler = STRING
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The compiler used to build Xen.
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#### /buildinfo/config = STRING [CONFIG_HYPFS_CONFIG]
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The contents of the `xen/.config` file at the time of the hypervisor build.
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#### /buildinfo/version/
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A directory containing version information of the hypervisor.
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#### /buildinfo/version/extra = STRING
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Extra version information.
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#### /buildinfo/version/major = INTEGER
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The major version of Xen.
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#### /buildinfo/version/minor = INTEGER
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The minor version of Xen.
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#### /params/
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A directory of runtime parameters.
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#### /params/*
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The individual parameters. The description of the different parameters can be
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found in `docs/misc/xen-command-line.pandoc`.
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