[Xen-devel] [PATCH v4 0/6] save/restore on Xen

[Stefano Stabellini <Stefano.Stabellini@xxxxxxxxxxxxx>]

Hi all,
this is the fourth version of the Xen save/restore patch series.
We have been discussing this issue for quite a while on #qemu and
qemu-devel:


http://marc.info/?l=qemu-devel&m=132346828427314&w=2
http://marc.info/?l=qemu-devel&m=132377734605464&w=2


A few different approaches were proposed to achieve the goal
of a working save/restore with upstream Qemu on Xen, however after
prototyping some of them I came up with yet another solution, that I
think leads to the best results with the less amount of code
duplications and ugliness.
Far from saying that this patch series is an example of elegance and
simplicity, but it is closer to acceptable anything else I have seen so
far.

What's new is that Qemu is going to keep track of its own physmap on
xenstore, so that Xen can be fully aware of the changes Qemu makes to
the guest's memory map at any time.
This is all handled by Xen or Xen support in Qemu internally and can be
used to solve our save/restore framebuffer problem.

>From the Qemu common code POV, we still need to avoid saving the guest's
ram when running on Xen, and we need to avoid resetting the videoram on
restore (that is a benefit to the generic Qemu case too, because it
saves few cpu cycles).


Changes in v4:

- keep a record of the MemoryRegion's name on xenstore;

- print a message when avoiding a memory allocation on restore.


This is the list of patches with a diffstat:

Anthony PERARD (4):
      vl.c: do not save the RAM state when Xen is enabled
      xen mapcache: check if memory region has moved.
      cirrus_vga: do not reset videoram on resume
      xen: change memory access behavior during migration.

Stefano Stabellini (2):
      Set runstate to INMIGRATE earlier
      xen: record physmap changes to xenstore

 hw/cirrus_vga.c |    9 +++-
 vl.c            |    8 ++-
 xen-all.c       |  112 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 xen-mapcache.c  |   22 +++++++++-
 xen-mapcache.h  |    9 +++-
 5 files changed, 147 insertions(+), 13 deletions(-)


git://xenbits.xen.org/people/sstabellini/qemu-dm.git saverestore-4

Cheers,

Stefano

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