tree 77bd673bc723fc2ed1155002b38cf5ad5d9c8cd5
parent c12784c3d14a2110468ec4d1383f60cfd2665576
author David Vrabel <david.vrabel@citrix.com> 1406820145 +0100
committer David Vrabel <david.vrabel@citrix.com> 1406825918 +0100

xen/events/fifo: ensure all bitops are properly aligned even on x86

When using the FIFO-based ABI on x86_64, if the last port is at the
end of an event array page then sync_test_bit() on this port's event
word will read beyond the end of the page and in certain circumstances
this may fault.

The fault requires the following page in the kernel's direct mapping
to be not present, which would mean:

a) the array page is the last page of RAM; or

b) the following page is ballooned out /and/ it has been used for a
   foreign mapping by a kernel driver (such as netback or blkback)
   /and/ the grant has been unmapped.

Use the infrastructure added for arm64 to ensure that all bitops
operating on event words are unsigned long aligned.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: stable@vger.kernel.org