debuggers.hg

changeset 22790:b01ef59c8c80

x86/mm: fix EPT PoD locking to match the normal p2m case.

This recursive-locking bug was fixed in the main p2m code in
20269:fd3d5d66c446 (in October 2009) but has lurked unseen in
the EPT side since then. Copy the fix across.

Signed-off-by: Tim Deegan <Tim.Deegan@citrix.com>
author Tim Deegan <Tim.Deegan@citrix.com>
date Thu Jan 13 15:46:13 2011 +0000 (2011-01-13)
parents 54e91dcae649
children 32b7a4f2d399
files xen/arch/x86/mm/hap/p2m-ept.c
line diff
     1.1 --- a/xen/arch/x86/mm/hap/p2m-ept.c	Thu Jan 13 15:38:48 2011 +0000
     1.2 +++ b/xen/arch/x86/mm/hap/p2m-ept.c	Thu Jan 13 15:46:13 2011 +0000
     1.3 @@ -45,19 +45,26 @@ static int ept_pod_check_and_populate(st
     1.4                                        ept_entry_t *entry, int order,
     1.5                                        p2m_query_t q)
     1.6  {
     1.7 +    /* Only take the lock if we don't already have it.  Otherwise it
     1.8 +     * wouldn't be safe to do p2m lookups with the p2m lock held */
     1.9 +    int do_locking = !p2m_locked_by_me(p2m);
    1.10      int r;
    1.11 -    p2m_lock(p2m);
    1.12 +
    1.13 +    if ( do_locking )
    1.14 +        p2m_lock(p2m);
    1.15  
    1.16      /* Check to make sure this is still PoD */
    1.17      if ( entry->sa_p2mt != p2m_populate_on_demand )
    1.18      {
    1.19 -        p2m_unlock(p2m);
    1.20 +        if ( do_locking )
    1.21 +            p2m_unlock(p2m);
    1.22          return 0;
    1.23      }
    1.24  
    1.25      r = p2m_pod_demand_populate(p2m, gfn, order, q);
    1.26  
    1.27 -    p2m_unlock(p2m);
    1.28 +    if ( do_locking )
    1.29 +        p2m_unlock(p2m);
    1.30  
    1.31      return r;
    1.32  }