1. 27 Oct, 2008 1 commit
    • Chris Lalancette's avatar
      xen: fix Xen domU boot with batched mprotect · 9f32d21c
      Chris Lalancette authored
      Impact: fix guest kernel boot crash on certain configs
      
      Recent i686 2.6.27 kernels with a certain amount of memory (between
      736 and 855MB) have a problem booting under a hypervisor that supports
      batched mprotect (this includes the RHEL-5 Xen hypervisor as well as
      any 3.3 or later Xen hypervisor).
      
      The problem ends up being that xen_ptep_modify_prot_commit() is using
      virt_to_machine to calculate which pfn to update.  However, this only
      works for pages that are in the p2m list, and the pages coming from
      change_pte_range() in mm/mprotect.c are kmap_atomic pages.  Because of
      this, we can run into the situation where the lookup in the p2m table
      returns an INVALID_MFN, which we then try to pass to the hypervisor,
      which then (correctly) denies the request to a totally bogus pfn.
      
      The right thing to do is to use arbitrary_virt_to_machine, so that we
      can be sure we are modifying the right pfn.  This unfortunately
      introduces a performance penalty because of a full page-table-walk,
      but we can avoid that penalty for pages in the p2m list by checking if
      virt_addr_valid is true, and if so, just doing the lookup in the p2m
      table.
      
      The attached patch implements this, and allows my 2.6.27 i686 based
      guest with 768MB of memory to boot on a RHEL-5 hypervisor again.
      Thanks to Jeremy for the suggestions about how to fix this particular
      issue.
      Signed-off-by: default avatarChris Lalancette <clalance@redhat.com>
      Signed-off-by: default avatarJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
      Cc: Chris Lalancette <clalance@redhat.com>
      Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      9f32d21c
  2. 26 Oct, 2008 29 commits
  3. 25 Oct, 2008 7 commits
  4. 24 Oct, 2008 3 commits