Let's add the basic infrastructure to exclude some physical memory
regions completely from /dev/mem access, on any architecture and under
any system configuration (independent of CONFIG_STRICT_DEVMEM and
independent of "iomem=").

Use it for virtio-mem, to disallow mapping any virtio-mem memory via
/dev/mem to user space after the virtio-mem driver was loaded: there is
no sane use case to access the device-managed memory region via /dev/mem
once the driver is actively (un)plugging memory within that region and
we want to make sure that nobody will accidentially access unplugged
memory in a sane environment.

Details can be found in patch #1.

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: "Rafael J. Wysocki" <redacted>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dan Williams <redacted>
Cc: Hanjun Guo <guohanjun@huawei.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: virtualization@lists.linux-foundation.org
Cc: linux-mm@kvack.org

David Hildenbrand (3):
  /dev/mem: disallow access to explicitly excluded system RAM regions
  virtio-mem: disallow mapping virtio-mem memory via /dev/mem
  kernel/resource: cleanup and optimize iomem_is_exclusive()

 drivers/char/mem.c          | 22 ++++++-------
 drivers/virtio/virtio_mem.c |  4 ++-
 include/linux/ioport.h      |  1 +
 kernel/resource.c           | 61 ++++++++++++++++++++++++++++++++-----
 lib/Kconfig.debug           |  4 ++-
 5 files changed, 69 insertions(+), 23 deletions(-)

-- 
2.31.1

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