On 16.08.21 16:25, David Hildenbrand wrote:

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.

v1 -> v2:
- "/dev/mem: disallow access to explicitly excluded system RAM regions"
-- Introduce and use for_each_resource() and next_resource_skip_children()
-- s/iomem_range_contains_excluded/iomem_range_contains_excluded_devmem/
- "kernel/resource: cleanup and optimize iomem_is_exclusive()"
-- Use for_each_resource()

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 <redacted>
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           | 60 +++++++++++++++++++++++++++++++++----
  lib/Kconfig.debug           |  4 ++-
  5 files changed, 71 insertions(+), 20 deletions(-)


base-commit: 7c60610d476766e128cc4284bb6349732cbd6606

More review welcome; I'd suggest this should go via the -mm tree, and 
not via the vhost tree.

-- 
Thanks,

David / dhildenb