xen: bug fixes for 3.17-rc4

- Fix for PVHVM suspend/resume and migration
- Don't pointlessly retry certain ballooning ops
- Fix gntalloc when grefs have run out.
- Fix PV boot if KSALR is enable or very large modules are used.
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.12 (GNU/Linux)

iQEcBAABAgAGBQJUEZw4AAoJEFxbo/MsZsTRoHkIAJ5h287Wer2Yf4ALlFI47Esl
AhcgVKi7WMJ6mBQUk/xpbSS3MZEuTuPJVbuiabJwRaZk9vX7w8q08yrAD8SOrCwY
6iGooaWEZ96P5DPI5fmWBuOgt5f2wfqzAp//wl/dK/kzr6Kw63huTXa0H0fmd8BY
Gy13pN4JEPDyvjjZWFvDcrcEUA9eTcTaXQZisBUGuGictXySr5ovz9G3EKOtJP0D
vkmDzApijFEEjJwZMGazgipng4mwh94fW4+7bs57s6iREpMzOJDTRKrl9suaXdza
5HA2ed7Au/qL8IwiQAFGxQpMBqNQxEGerlFfPBhRPuGQ+Ek3/pZF3BTU56w/nt4=
=y/Ol
-----END PGP SIGNATURE-----
x86/xen: don't copy bogus duplicate entries into kernel page tables

When RANDOMIZE_BASE (KASLR) is enabled; or the sum of all loaded
modules exceeds 512 MiB, then loading modules fails with a warning
(and hence a vmalloc allocation failure) because the PTEs for the
newly-allocated vmalloc address space are not zero.

  WARNING: CPU: 0 PID: 494 at linux/mm/vmalloc.c:128
           vmap_page_range_noflush+0x2a1/0x360()

This is caused by xen_setup_kernel_pagetables() copying
level2_kernel_pgt into level2_fixmap_pgt, overwriting many non-present
entries.

Without KASLR, the normal kernel image size only covers the first half
of level2_kernel_pgt and module space starts after that.

L4[511]->level3_kernel_pgt[510]->level2_kernel_pgt[  0..255]->kernel
                                                  [256..511]->module
                          [511]->level2_fixmap_pgt[  0..505]->module

This allows 512 MiB of of module vmalloc space to be used before
having to use the corrupted level2_fixmap_pgt entries.

With KASLR enabled, the kernel image uses the full PUD range of 1G and
module space starts in the level2_fixmap_pgt. So basically:

L4[511]->level3_kernel_pgt[510]->level2_kernel_pgt[0..511]->kernel
                          [511]->level2_fixmap_pgt[0..505]->module

And now no module vmalloc space can be used without using the corrupt
level2_fixmap_pgt entries.

Fix this by properly converting the level2_fixmap_pgt entries to MFNs,
and setting level1_fixmap_pgt as read-only.

A number of comments were also using the the wrong L3 offset for
level2_kernel_pgt.  These have been corrected.

Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: stable@vger.kernel.org
2 files changed