Filesystem passthrough "virtio-9pfs" support in KVM in RHEL7 ?

Latest response

Hi,
is this feature planned for RHEL7x KVM virtualization?

I checked the RHEL 7.0 and it's not there yet.

Thank you

ka
Log in to join the conversation

Responses

ka Active Contributor 246 points
4 July 2014 7:46 AM

Noone knows anything? :[ I'm not surprised though, i can't find any proper info around.

I'd like to do:
use the FS passthrough in scenario, where RHEL 7 insecure guest (facing to outworld internet) would have provided physical NIC from RHEL 7 host and thus, the KVM guest would be completely separated (sandboxed) from host machine networking.

I'd like to backup some files though to the host and the 9pfs seamed to me to be a way.

Sadly, in RHEL 7 there is even less support seamingly compared to RHEL 6 - there is not even kernel module compiled in natively:

cat /boot/config-3.10.0.-123.el7.x86_64 | grep -i 9p

CONFIG_NET_9P is not set

while e.g.

cat /boot/config-2.6.32-358.6.2.el6.x86_64 | grep -i 9p
CONFIG_NET_9P=m
CONFIG_NET_9P_VIRTIO=m
CONFIG_NET_9P_RDMA=m

CONFIG_NET_9P_DEBUG is not set

CONFIG_9P_FS is not set

So there is no plan to support this feature on RHEL 7? That remain total mystery to me and maybe even to RHEL devs? :]

David Powles's picture Red Hat 25369 points
8 July 2014 6:59 AM

Hi Karel. Sorry for the lack of response to this one. The long weekend in the US probably has something to do with that. ;)

I'll see if I can track down an answer for you.

ka Active Contributor 246 points
8 July 2014 1:52 PM

Thanks a lot!
I just wander, in Fedora it was introduced already some time ago, so i hoped, it might get at some point to RHEL7.
But as it looks atm., devs even removed the 'CONFIG_9P_FS' from RHEL7 kernel, which is quite discouraging move.
And no info to be found anywhere...

Thank for hlp,
cheers,

PB Red Hat Active Contributor 115 points
17 July 2014 2:33 PM

Hi Karel,

RHEL only provides a subset of kernel modules and QEMU device models, that are well tested and that Red Hat will be able to support for the 10 years of product lifetime. Unfortunately, virtio-9pfs does not satisfy these requirements yet:

  • it is not very well documented upstream, to the extent that it's hard to understand what works and what doesn't; the IBM team who worked on it moved to other tasks.

  • it has a privileged (setuid) component that may require special care in order to support SELinux and sVirt; the component is also not very well documented, which makes this problem worse;

  • it is not supported on Windows guests.

As of RHEL7, the recommended general-purpose file service is NFS; if it is not enough for your purpose, raising a
ticket through your regular Red Hat support channels will make your needs known to the support, product management and development teams.

I don't know the reason why CONFIG_9P_FS was enabled in RHEL6 and disabled in RHEL7; this was done independent of the choice to disable virtio-9pfs, and I wasn't involved in that decision.

ka Active Contributor 246 points
17 July 2014 3:05 PM

Thank You for valuable information.

Christian Labisch's picture Guru 9725 points
6 November 2016 3:54 PM

RHEL 7.3 just being released ... I realized that sharing files between hosts and guests using 9p ( http://www.linux-kvm.org/page/9p_virtio ) is still not possible. As 9p is a quite reliable and useful solution, I am wondering if there is a chance to have it included in the near future ?

PB Red Hat Active Contributor 115 points
7 November 2016 8:50 AM

Hi Christian,

my reply from two years ago is still valid, and explains why 9p is not as reliable as it seems. However, Red Hat is working on support for AF_VSOCK (virtio-vsock), so that NFS can be used between guests and hosts without interacting with e.g. the host and guest's firewall setup. In fact, this will be usable for more than just file system sharing.

We cannot really tell you yet when or if this will be included in RHEL, but for now there are copr packages for Fedora 24 at https://copr.fedorainfracloud.org/coprs/stefanha/vsock/packages/

You need at least the kernel (for both guest and host) and qemu-kvm packages.

For more info on how to run: http://qemu-project.org/Features/VirtioVsock

Christian Labisch's picture Guru 9725 points
7 November 2016 9:08 AM

Thank you for this information, Paolo ! :)

Close

Welcome! Check out the Getting Started with Red Hat page for quick tours and guides for common tasks.