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xen: add new hypercall buffer mapping device

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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>
This commit is contained in:
Juergen Gross
2018-06-18 09:36:39 +02:00
parent 7c63ca24c8
commit c51b3c639e
4 changed files with 223 additions and 1 deletions
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9
drivers/xen/privcmd.c
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@@ -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);