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.

This is a first implementation of that idea adding the basic
functionality to hypervisor and tools side. The interface to any
user program making use of that "xen-hypfs" is a new library
"libxenhypfs" with a stable interface.

As a followup switching libxl to use the hypervisor file system for
runtime parameter modifications is possible. This would enable
removal of the XEN_SYSCTL_set_parameter sysctl operation.

Changes in V3:
- major rework, especially by supporting binary contents of entries
- added several new patches (1, 2, 7)
- full support of all runtime parameters
- support of writing entries (especially runtime parameters)

Changes in V2:
- all comments to V1 addressed
- added man-page for xenhypfs tool
- added runtime parameter read access for string parameters

Changes in V1:
- renamed xenfs ->xenhypfs
- added writable entries support at the interface level and in the
  xenhypfs tool
- added runtime parameter read access (integer type only for now)
- added docs/misc/hypfs-paths.pandoc for path descriptions

Juergen Gross (9):
  xen: add a generic way to include binary files as variables
  xen: split parameter related definitions in own header file
  docs: add feature document for Xen hypervisor sysfs-like support
  xen: add basic hypervisor filesystem support
  libs: add libxenhypfs
  tools: add xenfs tool
  xen: provide version information in hypfs
  xen: add /buildinfo/config entry to hypervisor filesystem
  xen: add runtime parameter access support to hypfs

 .gitignore                               |   6 +
 docs/features/hypervisorfs.pandoc        |  86 +++++
 docs/man/xenhypfs.1.pod                  |  61 ++++
 docs/misc/hypfs-paths.pandoc             | 153 +++++++++
 tools/Rules.mk                           |   6 +
 tools/libs/Makefile                      |   1 +
 tools/libs/hypfs/Makefile                |  16 +
 tools/libs/hypfs/core.c                  | 535 +++++++++++++++++++++++++++++++
 tools/libs/hypfs/include/xenhypfs.h      |  75 +++++
 tools/libs/hypfs/libxenhypfs.map         |  10 +
 tools/libs/hypfs/xenhypfs.pc.in          |  10 +
 tools/misc/Makefile                      |   6 +
 tools/misc/xenhypfs.c                    | 189 +++++++++++
 xen/arch/arm/acpi/boot.c                 |   1 +
 xen/arch/arm/cpuerrata.c                 |   1 +
 xen/arch/arm/domain_build.c              |   1 +
 xen/arch/arm/gic-v3-lpi.c                |   1 +
 xen/arch/arm/setup.c                     |   1 +
 xen/arch/arm/smpboot.c                   |   1 +
 xen/arch/arm/traps.c                     |   2 +
 xen/arch/arm/xen.lds.S                   |   5 +
 xen/arch/x86/acpi/boot.c                 |   1 +
 xen/arch/x86/acpi/cpu_idle.c             |   1 +
 xen/arch/x86/acpi/cpufreq/cpufreq.c      |   1 +
 xen/arch/x86/acpi/power.c                |   1 +
 xen/arch/x86/apic.c                      |   1 +
 xen/arch/x86/cpu/amd.c                   |   1 +
 xen/arch/x86/cpu/common.c                |   1 +
 xen/arch/x86/cpu/mcheck/mce.c            |   1 +
 xen/arch/x86/cpu/mcheck/mce_intel.c      |   1 +
 xen/arch/x86/cpu/mtrr/generic.c          |   1 +
 xen/arch/x86/cpu/mwait-idle.c            |   1 +
 xen/arch/x86/cpu/vpmu.c                  |   1 +
 xen/arch/x86/cpuid.c                     |   1 +
 xen/arch/x86/dom0_build.c                |   1 +
 xen/arch/x86/e820.c                      |   1 +
 xen/arch/x86/genapic/probe.c             |   1 +
 xen/arch/x86/genapic/x2apic.c            |   1 +
 xen/arch/x86/hpet.c                      |   1 +
 xen/arch/x86/hvm/asid.c                  |   1 +
 xen/arch/x86/hvm/hvm.c                   |   1 +
 xen/arch/x86/hvm/hypercall.c             |   1 +
 xen/arch/x86/hvm/quirks.c                |   1 +
 xen/arch/x86/hvm/viridian/viridian.c     |   1 +
 xen/arch/x86/hvm/vmx/vmcs.c              |  18 +-
 xen/arch/x86/hvm/vmx/vmx.c               |   1 +
 xen/arch/x86/hypercall.c                 |   1 +
 xen/arch/x86/io_apic.c                   |   1 +
 xen/arch/x86/irq.c                       |   1 +
 xen/arch/x86/microcode.c                 |   1 +
 xen/arch/x86/mm.c                        |   1 +
 xen/arch/x86/mm/p2m.c                    |   1 +
 xen/arch/x86/msi.c                       |   1 +
 xen/arch/x86/nmi.c                       |   1 +
 xen/arch/x86/numa.c                      |   1 +
 xen/arch/x86/oprofile/nmi_int.c          |   1 +
 xen/arch/x86/psr.c                       |   1 +
 xen/arch/x86/pv/domain.c                 |   8 +-
 xen/arch/x86/pv/hypercall.c              |   1 +
 xen/arch/x86/pv/shim.c                   |   1 +
 xen/arch/x86/setup.c                     |   1 +
 xen/arch/x86/shutdown.c                  |   1 +
 xen/arch/x86/spec_ctrl.c                 |   1 +
 xen/arch/x86/tboot.c                     |   1 +
 xen/arch/x86/time.c                      |   1 +
 xen/arch/x86/traps.c                     |   1 +
 xen/arch/x86/tsx.c                       |   1 +
 xen/arch/x86/x86_64/mmconfig-shared.c    |   1 +
 xen/arch/x86/xen.lds.S                   |   5 +
 xen/arch/x86/xstate.c                    |   1 +
 xen/common/Makefile                      |  13 +
 xen/common/argo.c                        |   1 +
 xen/common/core_parking.c                |   1 +
 xen/common/cpupool.c                     |   1 +
 xen/common/debugtrace.c                  |   1 +
 xen/common/domain.c                      |   1 +
 xen/common/efi/boot.c                    |   1 +
 xen/common/gdbstub.c                     |   1 +
 xen/common/grant_table.c                 |  18 +-
 xen/common/hypfs.c                       | 403 +++++++++++++++++++++++
 xen/common/kernel.c                      |  79 ++++-
 xen/common/kexec.c                       |   1 +
 xen/common/memory.c                      |   1 +
 xen/common/page_alloc.c                  |   1 +
 xen/common/rcupdate.c                    |   1 +
 xen/common/sched_credit.c                |   1 +
 xen/common/sched_credit2.c               |   1 +
 xen/common/schedule.c                    |   1 +
 xen/common/shutdown.c                    |   1 +
 xen/common/timer.c                       |   1 +
 xen/common/trace.c                       |   1 +
 xen/drivers/acpi/apei/hest.c             |   1 +
 xen/drivers/acpi/tables.c                |   1 +
 xen/drivers/char/arm-uart.c              |   1 +
 xen/drivers/char/console.c               |  50 ++-
 xen/drivers/char/ehci-dbgp.c             |   1 +
 xen/drivers/char/ns16550.c               |   1 +
 xen/drivers/char/serial.c                |   1 +
 xen/drivers/cpufreq/cpufreq.c            |   1 +
 xen/drivers/passthrough/amd/iommu_acpi.c |   1 +
 xen/drivers/passthrough/iommu.c          |   1 +
 xen/drivers/passthrough/pci.c            |   1 +
 xen/drivers/passthrough/vtd/dmar.c       |   1 +
 xen/drivers/passthrough/vtd/quirks.c     |   1 +
 xen/drivers/passthrough/vtd/x86/vtd.c    |   1 +
 xen/drivers/passthrough/x86/ats.c        |   1 +
 xen/drivers/video/vesa.c                 |   1 +
 xen/drivers/video/vga.c                  |   1 +
 xen/include/public/hypfs.h               | 124 +++++++
 xen/include/public/xen.h                 |   1 +
 xen/include/xen/hypercall.h              |   8 +
 xen/include/xen/hypfs.h                  |  93 ++++++
 xen/include/xen/init.h                   | 120 -------
 xen/include/xen/kernel.h                 |   3 +
 xen/include/xen/param.h                  | 184 +++++++++++
 xen/tools/binfile                        |  29 ++
 xen/xsm/flask/Makefile                   |   5 +-
 xen/xsm/flask/flask-policy.S             |  16 -
 xen/xsm/flask/flask_op.c                 |   1 +
 xen/xsm/xsm_core.c                       |   1 +
 120 files changed, 2274 insertions(+), 151 deletions(-)
 create mode 100644 docs/features/hypervisorfs.pandoc
 create mode 100644 docs/man/xenhypfs.1.pod
 create mode 100644 docs/misc/hypfs-paths.pandoc
 create mode 100644 tools/libs/hypfs/Makefile
 create mode 100644 tools/libs/hypfs/core.c
 create mode 100644 tools/libs/hypfs/include/xenhypfs.h
 create mode 100644 tools/libs/hypfs/libxenhypfs.map
 create mode 100644 tools/libs/hypfs/xenhypfs.pc.in
 create mode 100644 tools/misc/xenhypfs.c
 create mode 100644 xen/common/hypfs.c
 create mode 100644 xen/include/public/hypfs.h
 create mode 100644 xen/include/xen/hypfs.h
 create mode 100644 xen/include/xen/param.h
 create mode 100755 xen/tools/binfile
 delete mode 100644 xen/xsm/flask/flask-policy.S

-- 
2.16.4


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On Jan 21, 2020, at 03:45, Juergen Gross <jgross@suse.com> wrote:
> 
> 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.

Is there a short summary of the most recent use cases for this feature and expected interactions with other Xen features (e.g. Panopticon Xen, security controls on information that is visible to guests, e.g. recent discussion on version number hiding). This would impact many subsystems.

Presumably Kconfig could enable/disable this optional feature and all dependencies, and the Xen toolstack would continue to function normally in its absence.

Rich
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On 26.01.20 23:05, Rich Persaud wrote:
> On Jan 21, 2020, at 03:45, Juergen Gross <jgross@suse.com> wrote:
>>
>> 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.
> 
> Is there a short summary of the most recent use cases for this feature and expected interactions with other Xen features (e.g. Panopticon Xen, security controls on information that is visible to guests, e.g. recent discussion on version number hiding). This would impact many subsystems.

In the first run access is permitted to dom0 only. Access to other
guests needs to be discussed.

Current use cases are just the buildinfo leafs including the .config
of the hypervisor, plus reading and writing runtime parameters.

I'd like to add per-cpupool parameters (like SMT per cpupool,
scheduling granularity) and maybe per-domain ones (e.g. mitigation
settings). Another area to cover would be debugging interfaces like
lock profiling, performance counters, ...

> Presumably Kconfig could enable/disable this optional feature and all dependencies, and the Xen toolstack would continue to function normally in its absence.

I'd rather go the other way round: have a detailed look which current
privileged interfaces (domctl, sysctl) can be replaced by the file
system and switch over to it with (where necessary) fine grained
access control. I think this is something to discuss at the next Xen
summit in summer (I have already registered a session for that
purpose).


Juergen


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