tree 8a156dfa0e0e4fca0e54a8f344d4767557e24c05
parent 7c63ca24c878e0051c91904b72174029320ef4bd
author Juergen Gross <jgross@suse.com> 1529307399 +0200
committer Juergen Gross <jgross@suse.com> 1529648802 +0200

xen: add new hypercall buffer mapping device

For passing arbitrary data from user land to the Xen hypervisor the
Xen tools today are using mlock()ed buffers. Unfortunately the kernel
might change access rights of such buffers for brief periods of time
e.g. for page migration or compaction, leading to access faults in the
hypervisor, as the hypervisor can't use the locks of the kernel.

In order to solve this problem add a new device node to the Xen privcmd
driver to easily allocate hypercall buffers via mmap(). The memory is
allocated in the kernel and just mapped into user space. Marked as
VM_IO the user mapping will not be subject to page migration et al.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>