[PATCHv9 0/9] Xen: extend kexec hypercall for use with pv-ops kernels

[David Vrabel <david.vrabel@citrix.com>]

The series (for Xen 4.4) improves the kexec hypercall by making Xen
responsible for loading and relocating the image.  This allows kexec
to be usable by pv-ops kernels and should allow kexec to be usable
from a HVM or PVH privileged domain.

The first patch is a simple clean-up.

Patch 2 introduces the new ABI.

Patch 3 and 4 nearly completely reimplement the kexec load, unload and
exec sub-ops.  The old load_v1 sub-op is then implemented on top of
the new code.

Patch 5 calls the kexec image when dom0 crashes.  This avoids having
to alter dom0 kernels to do a exec sub-op call on crash -- a
SHUTDOWN_crash by dom0 will trigger the kexec.

Patches 6 and 7 add the libxc API for the kexec calls.  These have
been acked-by Ian Campbell already.

Patch 8 adds a link time check for the size of the relocate code.

Patch 9 adds myself as the maintainer for kexec in Xen.

The required patch series for kexec-tools will be posted shortly and
are available from the xen-v6 branch of:

http://xenbits.xen.org/gitweb/?p=people/dvrabel/kexec-tools.git;a=summary

Changes in v9:

- Update comments to correctly say 4.4.
- Minor updates the kexec_reloc assembly to improve maintainability a
  bit.

Changes in v8:

- Use #defines for compat ABI structures.
- Tweak link time check for kexec_reloc.

Changes in v7:

- No longer use GUEST_HANDLE_64(), get a uniform ABI by using unions
  and explicit padding.
- Only map the segments and not all of RAM.
- Add a mechanism to create mappings for use by the exec'd image (a
  segment with a NULL buf handle).
- Fix a bug where a crash image's code page would by placed at machine
  address 0 (instead of inside the crash region).

Changes in v6:

- Fix double free in KEXEC_load_v1 failure path.
- Only copy the relocation code and not the whole page.
- Add myself as the kexec maintainer.

Changes in v5 (not posted to the list):

- _rsvd -> _pad in one of the public ABI structures.
- Fix bug where trailing pages were not zeroed. This fixes loading a
  64-bit Linux kernel using a more recent version of kexec-tools.
- Check the relocation code fits into a page at link time.

Changes in v4:

- Use paddr_t and page_to_maddr() etc. for portability.
- Add explicit padding to hypercall structures where required.
- Minor cleanup of the kexec_reloc assembly.
- Print a message before exec'ing a crash image.
- Style fixes (tabs, trailing whitespace) and typos.
- Fix a bug where using the V1 interface and unloading a image may crash.

Changes in v3:

- Provide old struct xen_kexec_load if __XEN_INTERFACE_VERSION__ < 4.3
- Adjust new struct xen_kexec_load to avoid unnecessary padding.
- Use domheap pages for the image and control pages.
- Remove the DBG() macros from the reloc code.

David