x86: ignore spurious faults
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 <b3f594e10a9edcf5413cf1190121d45078c62290@xensource.com>
Cc: Harvey Harrison <eadbd6b462bf3c97df0300a934c12bc2e5d1fe51@gmail.com>
Signed-off-by: Ingo Molnar <9dbbbf0688fedc85ad4da37637f1a64b8c718ee2@elte.hu>
Signed-off-by: Thomas Gleixner <00e4cf8f46a57000a44449bf9dd8cbbcc209fd2a@linutronix.de>

TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs