From c51b3c639e01f20559531eef3c5919feae23c55a Mon Sep 17 00:00:00 2001 From: Juergen Gross Date: Mon, 18 Jun 2018 09:36:39 +0200 Subject: 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 Reviewed-by: Boris Ostrovsky Signed-off-by: Juergen Gross --- drivers/xen/privcmd.c | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'drivers/xen/privcmd.c') diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c index 8ae0349d9f0a..7e6e682104dc 100644 --- a/drivers/xen/privcmd.c +++ b/drivers/xen/privcmd.c @@ -1007,12 +1007,21 @@ static int __init privcmd_init(void) pr_err("Could not register Xen privcmd device\n"); return err; } + + err = misc_register(&xen_privcmdbuf_dev); + if (err != 0) { + pr_err("Could not register Xen hypercall-buf device\n"); + misc_deregister(&privcmd_dev); + return err; + } + return 0; } static void __exit privcmd_exit(void) { misc_deregister(&privcmd_dev); + misc_deregister(&xen_privcmdbuf_dev); } module_init(privcmd_init); -- cgit v1.2.3