Hello, I want to ask if XEN use TUP/TAP interfaces or use other interface? I know that linux uses these interfaces and I suppose that most of virtual machine too, because they are based on linux architecture, isn''t true? Do you think that VirtualBox uses TUN/TAP? I know, this question is for members of VirtualBox mailing list, but if you know it so I will happy. Thanks for your advise. Regards Pavel _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
On Sun, 2008-03-16 at 15:52 +0100, Pavel Muller wrote:> Hello, > I want to ask if XEN use TUP/TAP interfaces or use other interface?No. TUN/TAP is typically used for hosted VMs. Broadly speaking, it''s only useful if a significant part of the VMM is running in user mode on top of a native Linux, as is the case with VMware Workstation, VirtualBox, UserModeLinux etc. Xen is a hypervisor, running below all OSes on bare hardware. The network virtualization is based on a Linux OS (dom0), but the guests aren''t running on top of that, but rather as siblings on a common virtualization layer. There''s a dedicated interface class (vifN.M) in dom0. The purpose is similar, but the interplay with guests is quite a different one.> I know that linux uses these interfaces and I suppose that most of > virtual machine too, because they are based on linux architecture, > isn''t true? Do you think that VirtualBox uses TUN/TAP? I know, this > question is for members of VirtualBox mailing list, but if you know it > so I will happy. Thanks for your advise.hth, Daniel -- Daniel Stodden LRR - Lehrstuhl für Rechnertechnik und Rechnerorganisation Institut für Informatik der TU München D-85748 Garching http://www.lrr.in.tum.de/~stodden mailto:stodden@cs.tum.edu PGP Fingerprint: F5A4 1575 4C56 E26A 0B33 3D80 457E 82AE B0D8 735B _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
On Sun, 2008-03-16 at 17:50 +0100, Daniel Stodden wrote:> No. TUN/TAP is typically used for hosted VMs. Broadly speaking, it''s > only useful if a significant part of the VMM is running in user mode on > top of a native Linux, as is the case with VMware Workstation,BTW: don''t get me wrong: VMware isn''t using TUN/TAP, just hosted. VirtualBox can use TUN/TAP, but the default vbox setup for a simple desktop VM is typically NAT. Via a custom kernel module, which does not create a dedicated host interface. Daniel -- Daniel Stodden LRR - Lehrstuhl für Rechnertechnik und Rechnerorganisation Institut für Informatik der TU München D-85748 Garching http://www.lrr.in.tum.de/~stodden mailto:stodden@cs.tum.edu PGP Fingerprint: F5A4 1575 4C56 E26A 0B33 3D80 457E 82AE B0D8 735B _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
On Sun, Mar 16, 2008 at 05:50:19PM +0100, Daniel Stodden wrote:> On Sun, 2008-03-16 at 15:52 +0100, Pavel Muller wrote: > > Hello, > > I want to ask if XEN use TUP/TAP interfaces or use other interface? > > No. TUN/TAP is typically used for hosted VMs. Broadly speaking, it''s > only useful if a significant part of the VMM is running in user mode on > top of a native Linux, as is the case with VMware Workstation, > VirtualBox, UserModeLinux etc. > > Xen is a hypervisor, running below all OSes on bare hardware. The > network virtualization is based on a Linux OS (dom0), but the guests > aren''t running on top of that, but rather as siblings on a common > virtualization layer.Whether it is a separate hypervisor / Dom0, or a combined HV+Dom0 is not really relevant to this question. In both cases the driver backends are in the Linux host OS and not the hypervisor itself.> > There''s a dedicated interface class (vifN.M) in dom0. The purpose is > similar, but the interplay with guests is quite a different one.This is correct for paravirt guest or PV drivers, but is wrong for fullvirt. The QEMU device model used for fullvirt guests *does* use TUN/TAP devices as the backend for its emulated ne2k/rtl8139 NICs. Dan. -- |: Red Hat, Engineering, Boston -o- http://people.redhat.com/berrange/ :| |: http://libvirt.org -o- http://virt-manager.org -o- http://ovirt.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: GnuPG: 7D3B9505 -o- F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :| _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
On Sun, 2008-03-16 at 17:12 +0000, Daniel P. Berrange wrote:> On Sun, Mar 16, 2008 at 05:50:19PM +0100, Daniel Stodden wrote: > > On Sun, 2008-03-16 at 15:52 +0100, Pavel Muller wrote: > > > Hello, > > > I want to ask if XEN use TUP/TAP interfaces or use other interface? > > > > No. TUN/TAP is typically used for hosted VMs. Broadly speaking, it''s > > only useful if a significant part of the VMM is running in user mode on > > top of a native Linux, as is the case with VMware Workstation, > > VirtualBox, UserModeLinux etc. > > > > Xen is a hypervisor, running below all OSes on bare hardware. The > > network virtualization is based on a Linux OS (dom0), but the guests > > aren''t running on top of that, but rather as siblings on a common > > virtualization layer. > > Whether it is a separate hypervisor / Dom0, or a combined HV+Dom0 is not > really relevant to this question. In both cases the driver backends are > in the Linux host OS and not the hypervisor itself.Using TUN/TAP is absolutely pointless if the peer is not running in userland. Because connecting userspace to a network interface is the whole point there. And this is why the VMM type matters to answer the question.> > There''s a dedicated interface class (vifN.M) in dom0. The purpose is > > similar, but the interplay with guests is quite a different one. > > This is correct for paravirt guest or PV drivers, but is wrong for fullvirt. > The QEMU device model used for fullvirt guests *does* use TUN/TAP devices > as the backend for its emulated ne2k/rtl8139 NICs.Oh, I did not think about HVM, you''re right. But that is a special case which is different from most other solutions out there. regards, daniel -- Daniel Stodden LRR - Lehrstuhl für Rechnertechnik und Rechnerorganisation Institut für Informatik der TU München D-85748 Garching http://www.lrr.in.tum.de/~stodden mailto:stodden@cs.tum.edu PGP Fingerprint: F5A4 1575 4C56 E26A 0B33 3D80 457E 82AE B0D8 735B _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
On Sun, Mar 16, 2008 at 06:21:51PM +0100, Daniel Stodden wrote:> On Sun, 2008-03-16 at 17:12 +0000, Daniel P. Berrange wrote: > > On Sun, Mar 16, 2008 at 05:50:19PM +0100, Daniel Stodden wrote: > > > On Sun, 2008-03-16 at 15:52 +0100, Pavel Muller wrote: > > > > Hello, > > > > I want to ask if XEN use TUP/TAP interfaces or use other interface? > > > > > > No. TUN/TAP is typically used for hosted VMs. Broadly speaking, it''s > > > only useful if a significant part of the VMM is running in user mode on > > > top of a native Linux, as is the case with VMware Workstation, > > > VirtualBox, UserModeLinux etc. > > > > > > Xen is a hypervisor, running below all OSes on bare hardware. The > > > network virtualization is based on a Linux OS (dom0), but the guests > > > aren''t running on top of that, but rather as siblings on a common > > > virtualization layer. > > > > Whether it is a separate hypervisor / Dom0, or a combined HV+Dom0 is not > > really relevant to this question. In both cases the driver backends are > > in the Linux host OS and not the hypervisor itself. > > Using TUN/TAP is absolutely pointless if the peer is not running in > userland. Because connecting userspace to a network interface is the > whole point there. > > And this is why the VMM type matters to answer the question.No the distinction here is between kernel space & user space backends, not between host OS and hypervisor. The hypervisor doesn''t get involved in the driver backends - it is delegated to the host OS to take care of. Dan. -- |: Red Hat, Engineering, Boston -o- http://people.redhat.com/berrange/ :| |: http://libvirt.org -o- http://virt-manager.org -o- http://ovirt.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: GnuPG: 7D3B9505 -o- F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :| _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
On Sun, 2008-03-16 at 17:41 +0000, Daniel P. Berrange wrote:> > > Whether it is a separate hypervisor / Dom0, or a combined HV+Dom0 is not > > > really relevant to this question. In both cases the driver backends are > > > in the Linux host OS and not the hypervisor itself. > > > > Using TUN/TAP is absolutely pointless if the peer is not running in > > userland. Because connecting userspace to a network interface is the > > whole point there. > > > > And this is why the VMM type matters to answer the question. > > No the distinction here is between kernel space & user space backends, not > between host OS and hypervisor. The hypervisor doesn''t get involved in the > driver backends - it is delegated to the host OS to take care of.Okay, you''re certainly right. I hereby correct myself: TUN/TAP is used when the VMM part doing I/O virtualization is in userspace. Whether the part of the VMM doing I/O virtualization ends up as userspace on a UNIX system with TUN/TAP support depends on the VMM type, with the exception of a type I VMM which is quite different from a typical type I VMM in that it is delegating I/O virtualization to a guest OS running QEMU. Much better, thank you. Kind Regards, Daniel -- Daniel Stodden LRR - Lehrstuhl für Rechnertechnik und Rechnerorganisation Institut für Informatik der TU München D-85748 Garching http://www.lrr.in.tum.de/~stodden mailto:stodden@cs.tum.edu PGP Fingerprint: F5A4 1575 4C56 E26A 0B33 3D80 457E 82AE B0D8 735B _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel