xen/arm: do not setup the runstate info page if kpti is enabled

The VCPUOP_register_runstate_memory_area hypercall takes a virtual
address of a buffer as a parameter. The semantics of the hypercall are
such that the virtual address should always be valid.

When KPTI is enabled and we are running userspace code, the virtual
address is not valid, thus, Linux is violating the semantics of
VCPUOP_register_runstate_memory_area.

Do not call VCPUOP_register_runstate_memory_area when KPTI is enabled.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com>
CC: Bertrand Marquis <Bertrand.Marquis@arm.com>
CC: boris.ostrovsky@oracle.com
CC: jgross@suse.com
Link: https://lore.kernel.org/r/20200924234955.15455-1-sstabellini@kernel.org
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

arm/arm64: xen: Move shared architecture headers to include/xen/arm

ARM and arm64 Xen ports share a number of headers, leading to
packaging issues when these headers needs to be exported, as it
breaks the reasonable requirement that an architecture port
has self-contained headers.

Fix the issue by moving the 5 header files to include/xen/arm,
and keep local placeholders to include the relevant files.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

arm64/xen: introduce asm/xen header files on arm64

asm/xen/hypercall.h, asm/xen/hypervisor.h, asm/xen/interface.h and
asm/xen/page.h are identical so to avoid code duplication we are just
including the original arm header files here.

asm/xen/events.h is slightly different, so introduce a different file
here (use xchg to implement xchg_xen_ulong and pass regs->pstate to
raw_irqs_disabled_flags).

Also introduce asm/hypervisor.h and asm/sync_bitops.h.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>