x86: ignore spurious faults
authorJeremy Fitzhardinge <jeremy@goop.org>
Wed, 30 Jan 2008 12:34:11 +0000 (13:34 +0100)
committerIngo Molnar <mingo@elte.hu>
Wed, 30 Jan 2008 12:34:11 +0000 (13:34 +0100)
commit5b727a3b0158a129827c21ce3bfb0ba997e8ddd0
treee0d43e258fa46e22ac6c4daf82c5005dc0e762c6
parentb406ac61e94875723540bd56e26f634afdeef489
x86: ignore spurious faults

When changing a kernel page from RO->RW, it's OK to leave stale TLB
entries around, since doing a global flush is expensive and they pose
no security problem.  They can, however, generate a spurious fault,
which we should catch and simply return from (which will have the
side-effect of reloading the TLB to the current PTE).

This can occur when running under Xen, because it frequently changes
kernel pages from RW->RO->RW to implement Xen's pagetable semantics.
It could also occur when using CONFIG_DEBUG_PAGEALLOC, since it avoids
doing a global TLB flush after changing page permissions.

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
arch/x86/mm/fault.c