Karel Hendrych
2015-Sep-07 15:42 UTC
[CentOS-virt] libvirt, xen PV, qemu-system-i386, root user
Hi, spot on! On 6.9.2015 12:56, Pasi K?rkk?inen wrote:> On Sun, Sep 06, 2015 at 09:08:50AM +0200, Karel Hendrych wrote: >> Hi, after migrating to libvirt/libxl according to: >> > > Hi, > >> https://wiki.centos.org/HowTos/Xen/Xen4QuickStart/Xen4Libvirt >> >> I've noticed that my Xen PV domains are being launched by >> qemu-system-i386 running under root privileges. >> >> I am wondering why is this? Previously no qemu process was used. >> >> If qemu is needed for some reason, are there any guidelines for >> non-root operation? >> > > In general qemu is used for the following purposes: > > - for certain domU disk backend types (image files), and/or if there's no blktap driver in dom0 kernel. > - domU graphical console (PVFB) VNC server, if it's enabled for the domU. > > >> -- >> Karel Hendrych > > > -- Pasi > > _______________________________________________ > CentOS-virt mailing list > CentOS-virt at centos.org > https://lists.centos.org/mailman/listinfo/centos-virt >
Karel Hendrych
2015-Sep-07 15:47 UTC
[CentOS-virt] libvirt, xen PV, qemu-system-i386, root user
... changing from: <driver name='file'/> to: <driver name='tap2'/> makes the domain start without QEMU. However I see much better performance with QEMU (close to dom0, tested using simple dd writes) than with tap2 driver. Is that expected? What's best practise to file based storage on latest CentOS6-xen (Kernel 3.18.17, Xen 4.4.2-7) Are there any guides around running QEMU on CentOS6-xen as non-root user? Cheers -- Karel On 7.9.2015 17:42, Karel Hendrych wrote:> Hi, spot on! > > > On 6.9.2015 12:56, Pasi K?rkk?inen wrote: >> On Sun, Sep 06, 2015 at 09:08:50AM +0200, Karel Hendrych wrote: >>> Hi, after migrating to libvirt/libxl according to: >>> >> >> Hi, >> >>> https://wiki.centos.org/HowTos/Xen/Xen4QuickStart/Xen4Libvirt >>> >>> I've noticed that my Xen PV domains are being launched by >>> qemu-system-i386 running under root privileges. >>> >>> I am wondering why is this? Previously no qemu process was used. >>> >>> If qemu is needed for some reason, are there any guidelines for >>> non-root operation? >>> >> >> In general qemu is used for the following purposes: >> >> - for certain domU disk backend types (image files), and/or if there's >> no blktap driver in dom0 kernel. >> - domU graphical console (PVFB) VNC server, if it's enabled for the domU. >> >> >>> -- >>> Karel Hendrych >> >> >> -- Pasi >> >> _______________________________________________ >> CentOS-virt mailing list >> CentOS-virt at centos.org >> https://lists.centos.org/mailman/listinfo/centos-virt >>
Pasi Kärkkäinen
2015-Sep-07 19:45 UTC
[CentOS-virt] libvirt, xen PV, qemu-system-i386, root user
On Mon, Sep 07, 2015 at 05:47:39PM +0200, Karel Hendrych wrote:> ... > > changing from: <driver name='file'/> to: <driver name='tap2'/> makes > the domain start without QEMU. > > However I see much better performance with QEMU (close to dom0, > tested using simple dd writes) than with tap2 driver. Is that > expected? >How did you measure it? buffered or direct io? -- Pasi> What's best practise to file based storage on latest CentOS6-xen > (Kernel 3.18.17, Xen 4.4.2-7) > > Are there any guides around running QEMU on CentOS6-xen as non-root user? > > Cheers > -- > Karel > > On 7.9.2015 17:42, Karel Hendrych wrote: > >Hi, spot on! > > > > > >On 6.9.2015 12:56, Pasi K?rkk?inen wrote: > >>On Sun, Sep 06, 2015 at 09:08:50AM +0200, Karel Hendrych wrote: > >>>Hi, after migrating to libvirt/libxl according to: > >>> > >> > >>Hi, > >> > >>>https://wiki.centos.org/HowTos/Xen/Xen4QuickStart/Xen4Libvirt > >>> > >>>I've noticed that my Xen PV domains are being launched by > >>>qemu-system-i386 running under root privileges. > >>> > >>>I am wondering why is this? Previously no qemu process was used. > >>> > >>>If qemu is needed for some reason, are there any guidelines for > >>>non-root operation? > >>> > >> > >>In general qemu is used for the following purposes: > >> > >>- for certain domU disk backend types (image files), and/or if there's > >>no blktap driver in dom0 kernel. > >>- domU graphical console (PVFB) VNC server, if it's enabled for the domU. > >> > >> > >>>-- > >>>Karel Hendrych > >> > >> > >>-- Pasi > >> > >>_______________________________________________ > >>CentOS-virt mailing list > >>CentOS-virt at centos.org > >>https://lists.centos.org/mailman/listinfo/centos-virt > >> > _______________________________________________ > CentOS-virt mailing list > CentOS-virt at centos.org > https://lists.centos.org/mailman/listinfo/centos-virt