x86/hvm: treat non-instruction fetch nested page faults also as read violations

x86/hvm: treat non-instruction fetch nested page faults also as read violations

As pointed out by Jan Beulich in
http://lists.xen.org/archives/html/xen-devel/2014-08/msg01269.html:
"Read-modify-write instructions absolutely need to be treated as read
accesses, yet hardware doesn't guarantee to tell us so (they may
surface as just write accesses)." This patch addresses the issue in
both the VMX and the SVM side.

VMX: Treat all write data access violations also as read violations (in
     addition to those that were already reported as read violations).
SVM: Refine the meaning of read data access violations to distinguish
     between read/write and instruction fetch access violations.

With this patch both VMX and SVM specific nested page fault handling code reports violations the same way, thus abstracting the hardware specific behaviour from the layers above.

Suggested-by: Jan Beulich <JBeulich@suse.com>
Signed-off-by: Tamas K Lengyel <tamas.lengyel@zentific.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Tim Deegan <tim@xen.org>