Hi, from what I could find digging around, it is ok to run a 32-bit DomU with a 64bit Xen/Dom0 as long as you use linux32 to avoid the package utilities from trying to install 64 bit packages in the DomUs. What I''m not sure of is if you can run linux32 without modifying the DomU init scripts (by using initrd for example) so that the DomU never thinks it is running on a 64-bit arch. If you can do it with a custom initrd, I''d like to see one example. As anyone set up such an environment or knows such one? Lionel. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> -----Original Message----- > From: xen-users-bounces@lists.xensource.com > [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of > Lionel Bouton > Sent: 24 October 2006 16:14 > To: xen-users@lists.xensource.com > Subject: [Xen-users] 32bit DomuU on 64-bit Xen > > Hi, > > from what I could find digging around, it is ok to run a 32-bit DomU > with a 64bit Xen/Dom0 as long as you use linux32 to avoid the package > utilities from trying to install 64 bit packages in the DomUs.Ehm, no you CAN NOT run 32-bit DomU on a 64-bit Xen/Dom0, because all kernel modes must be the same (32-bit no PAE, 32-bit PAE or 64-bit).> > What I''m not sure of is if you can run linux32 without modifying the > DomU init scripts (by using initrd for example) so that the > DomU never > thinks it is running on a 64-bit arch. If you can do it with a custom > initrd, I''d like to see one example.You can, if you install a 64-bit kernel, run "linux32" when you install "stupid" applications that don''t understand that 32-bit binaries are supported by 64-bit. You shouldn''t have to do this in the "average" case, applications will "just work". But there are some rare exceptions that think that "If this isn''t an i[3456]86 archiecture, I''m not going to install". You will of course have to install 32-bit support-libraries (which is most often default in the distro anyways) - but it works just fine to do "rpm -i blah-x.y.z-i386.rpm" on a x86_64 machine - it will install the 32-bit version on your machine, and all will work just like you expect it to... -- Mats> > As anyone set up such an environment or knows such one? > > Lionel. > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users > > >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Petersson, Mats wrote the following on 24.10.2006 17:46 :> > > >> -----Original Message----- >> From: xen-users-bounces@lists.xensource.com >> [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of >> Lionel Bouton >> Sent: 24 October 2006 16:14 >> To: xen-users@lists.xensource.com >> Subject: [Xen-users] 32bit DomuU on 64-bit Xen >> >> Hi, >> >> from what I could find digging around, it is ok to run a 32-bit DomU >> with a 64bit Xen/Dom0 as long as you use linux32 to avoid the package >> utilities from trying to install 64 bit packages in the DomUs. >> > > Ehm, no you CAN NOT run 32-bit DomU on a 64-bit Xen/Dom0, because all > kernel modes must be the same (32-bit no PAE, 32-bit PAE or 64-bit). >What I thought was possible is to start the 32-bit DomU with a 64-bit kernel and use a custom initrd to call linux32 before /sbin/init -> the whole DomU could still be 32-bit, but the kernel would be 64-bit. I''m wondering if there could be problems with some userland system utilities like iptables though. Can''t this work? Lionel _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> -----Original Message----- > From: xen-users-bounces@lists.xensource.com > [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of > Lionel Bouton > Sent: 24 October 2006 18:22 > To: Petersson, Mats > Cc: xen-users@lists.xensource.com > Subject: Re: [Xen-users] 32bit DomU on 64-bit Xen > > Petersson, Mats wrote the following on 24.10.2006 17:46 : > > > > > > > >> -----Original Message----- > >> From: xen-users-bounces@lists.xensource.com > >> [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of > >> Lionel Bouton > >> Sent: 24 October 2006 16:14 > >> To: xen-users@lists.xensource.com > >> Subject: [Xen-users] 32bit DomuU on 64-bit Xen > >> > >> Hi, > >> > >> from what I could find digging around, it is ok to run a > 32-bit DomU > >> with a 64bit Xen/Dom0 as long as you use linux32 to avoid > the package > >> utilities from trying to install 64 bit packages in the DomUs. > >> > > > > Ehm, no you CAN NOT run 32-bit DomU on a 64-bit Xen/Dom0, > because all > > kernel modes must be the same (32-bit no PAE, 32-bit PAE or 64-bit). > > > > What I thought was possible is to start the 32-bit DomU with a 64-bit > kernel and use a custom initrd to call linux32 before > /sbin/init -> the > whole DomU could still be 32-bit, but the kernel would be 64-bit. I''m > wondering if there could be problems with some userland > system utilities > like iptables though.And the benefit of this is? I believe iptables is one of the things that you can''t run the 32-bit version on a 64-bit kernel - although I''m not sure... When googling on the subject, I found that there was a patch submitted in early January 2006 to "fix" this problem - whether that patch got accepted and works is a different question - I didn''t look at it further...> > Can''t this work?All user-mode code that doesn''t make assumptions about the kernel or uses pre-compiled 32-bit kernel modeuls can be run on 64-bit kernel - but again, what is the benefit of running a complete 32-bit installation that is NOT part of a packaged distribution, when there is a (hopefully) some distribution that comes with the complete 64-bit set of "guaranteed by the distributor to work together" parts - ok, so it may not ALWAYS work as the distributor says, but if you mix''n''match your own version of 32+64-bit parts, it''s almost guaranteed that you''re going to have SOME problems - at least the main distributors do put SOME effort into making sure what they distribut works... All compatibility problems caused by the kernel being 64-bit would still remain. The only point I can see is that you save some diskspace by only installing 32-bit .so''s, but with a limited installation of 64-bit tools, you''d not fill enough diskspace to REALLY make a huge difference. I just don''t get the point, so if you could enlighten me as to why you would want to do this, I''ll look further at any reason why it would/would not work... -- Mats> > Lionel > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users > > >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Petersson, Mats wrote the following on 24.10.2006 19:55 :> > All user-mode code that doesn''t make assumptions about the kernel or > uses pre-compiled 32-bit kernel modeuls can be run on 64-bit kernel - > but again, what is the benefit of running a complete 32-bit installation > that is NOT part of a packaged distribution,?!> when there is a (hopefully) > some distribution that comes with the complete 64-bit set of "guaranteed > by the distributor to work together" partsNow I understand. We *need* 32 bit environments, see below.> - ok, so it may not ALWAYS > work as the distributor says, but if you mix''n''match your own version of > 32+64-bit parts, it''s almost guaranteed that you''re going to have SOME > problems - at least the main distributors do put SOME effort into making > sure what they distribut works... > > All compatibility problems caused by the kernel being 64-bit would still > remain. The only point I can see is that you save some diskspace by only > installing 32-bit .so''s, but with a limited installation of 64-bit > tools, you''d not fill enough diskspace to REALLY make a huge difference. > > > I just don''t get the point, so if you could enlighten me as to why you > would want to do this, I''ll look further at any reason why it > would/would not work... >Software support. I work for a software publisher. We have several products which are (or will shortly be) available both for 64 and 32 bit environments. I don''t have HVM-capable hardware yet, mostly have 32 bit support environments and don''t want to install 32-bit Xen servers to start moving them to 64 bit in order to follow the market in the following years. So I''d like to run 32 bits DomUs on my Opteron servers now and 64-bit DomUs later (with a mix of them in between)... To put things more in context: we have a repository of DomUs (both compressed disk images and whole configuration for each DomU) on a dedicated (non Xen) server with a huge majority of 32bit DomUs (we don''t have 64-bit installations to support yet and are only moving 64 bit development environments to Xen) that are dynamically transferred to a Xen server. We use a small custom Xen admin console to handle our needs (distributing DomUs on tens of servers, helping our users choose the appropriate Xen server for their needs, managing DomU versioning, system-wide backup, ...). Currently when a client reports a problem in one of our software product, we check if the appropriate support environment for the software is up (based on the distribution it runs on and the actual software versions, we can have more than 10 environments for a single software product). If it isn''t we click a button in the Web UI or launch a script on the admin console to start it on one of the available Xen servers. We then try to reproduce the problem and use a development environment (other DomUs which are up most of the time) to correct it once we find the source. When updates from distributions used by our clients are available we make a new version of the appropriate support environments and check that these updates don''t break anything before giving our clients the green light (or handling the update ourselves depending on our contract with them). Currently all of this takes place on 32-bit environments. But this is already starting to change for the development and integration environments for which we use 64-bit distributions on top of 32-bit ones... The only thing that we left out of our support environment is the kernel (which can never be identical to the one of our clients because they don''t use Xen - yet - and even if we used HVM to run the same kernel we couldn''t actually support it because of the tiny device driver usage differences: the devil is in the details). We have custom built kernels and only create new kernels when one of our product environment needs it (when a configuration isn''t compatible with a new distribution or a kernel feature is lacking, which... never happened since we started using Xen). Anyway if the need for kernel-level support arise (it happens when the solution involves not only our sofware but interfaces with specific hardware), we simply request the client to pay for a full hardware support environment and this is obviously completely separated from the Xen environment. So using 64-bit kernels for 32-bit distributions doesn'' seem to be a problem for us (as long as there''s not an incompatibility between userspace and kernelspace, and I don''t think we have to support any incompatible userspace and will have to in the foreseeable future). Lionel _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Petersson, Mats wrote:> > Ehm, no you CAN NOT run 32-bit DomU on a 64-bit Xen/Dom0, because all > kernel modes must be the same (32-bit no PAE, 32-bit PAE or 64-bit).Just to cross-check my own understanding, this only applies to para-virtualized 32bit DomUs under a 64bit hypervisor host? Can HVM DomUs can be anything under the sun? _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> -----Original Message----- > From: Thomas Harold [mailto:tgh@tgharold.com] > Sent: 24 October 2006 21:27 > To: Petersson, Mats > Cc: xen-users@lists.xensource.com > Subject: Re: [Xen-users] 32bit DomuU on 64-bit Xen > > Petersson, Mats wrote: > > > > Ehm, no you CAN NOT run 32-bit DomU on a 64-bit Xen/Dom0, > because all > > kernel modes must be the same (32-bit no PAE, 32-bit PAE or > 64-bit). > > Just to cross-check my own understanding, this only applies to > para-virtualized 32bit DomUs under a 64bit hypervisor host? Can HVM > DomUs can be anything under the sun?As long as the hypervisor/Dom0 is "better" than the HVM guest, yes. So if you want to be able to "run anything", you should use a 64-bit Xen/Dom0. -- Mats _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users