mbox series

[v2,0/3] vhost-user: warn when guest RAM is not shared

Message ID 20210525142803.125401-1-stefanha@redhat.com (mailing list archive)
Headers show
Series vhost-user: warn when guest RAM is not shared | expand

Message

Stefan Hajnoczi May 25, 2021, 2:28 p.m. UTC
v2:
 * Clarify that object-memory-memfd enables share=on by default [Marc-André]
 * Rebased

vhost-user requires -object memory-backend-*,share=on option so that QEMU uses
mmap(MAP_SHARED) on guest RAM that is shared with the vhost-user device backend
process. This is needed so the QEMU process sees changes made by the vhost-user
device backend process, and vice versa.

Today QEMU and the vhost-user device process will start up and then fail with a
confusing error message if the user forgot to specify share=on.

This patch series adds a warning letting the user know that share=on is
required.

Stefan Hajnoczi (3):
  tests/qtest/vhost-user-test: use share=on with memfd
  memory: add memory_region_is_mapped_shared()
  vhost-user: warn when guest RAM is not shared

 include/exec/memory.h         | 11 +++++++++++
 hw/virtio/vhost-user.c        | 20 ++++++++++++++++----
 softmmu/memory.c              |  6 ++++++
 tests/qtest/vhost-user-test.c |  2 +-
 4 files changed, 34 insertions(+), 5 deletions(-)