Hi, We are working on DAX support in virtiofs and have some patches out of the tree hosted here.
https://gitlab.com/virtio-fs/qemu/-/commits/virtio-fs-dev These patches have not been proposed for merge yet, becasue David Gilbert noticed that we can run into a deadlock during an emergency reboot of guest kernel. (echo b > /proc/sysrq-trigger). I have provided details of deadlock in 4th path of the series with subject "qemu, vhost-user: Extend protocol to start/stop/flush slave channel". Basic problem seems to be that we don't have a proper mechanism to shutdown slave channel when vhost-user device is stopping. This means there might be pending messages in slave channel and slave is blocked and waiting for response. This is an RFC patch series to enhance vhost-user protocol to properly shutdown/flush slave channel and avoid the deadlock. Though we faced the issue in the context of virtiofs, any vhost-user device using slave channel can potentially run into issues and can benefit from these patches. Any feedback is welcome. Currently patches are based on out of tree code but after I get some feedback, I can only take pieces which are relevant to upstream and post separately. Thanks Vivek Vivek Goyal (6): virtiofsd: Drop ->vu_dispatch_rwlock while waiting for thread to exit libvhost-user: Use slave_mutex in all slave messages vhost-user: Return error code from slave_read() qemu, vhost-user: Extend protocol to start/stop/flush slave channel libvhost-user: Add support to start/stop/flush slave channel virtiofsd: Opt in for slave start/stop/shutdown functionality hw/virtio/vhost-user.c | 151 +++++++++++++++++++++- subprojects/libvhost-user/libvhost-user.c | 147 +++++++++++++++++---- subprojects/libvhost-user/libvhost-user.h | 8 +- tools/virtiofsd/fuse_virtio.c | 20 +++ 4 files changed, 294 insertions(+), 32 deletions(-) -- 2.25.4