From: Russell R. <rus...@op...> - 2007-03-01 21:23:54
|
Hi, This is a list of what I've learned so far about UML. I'm simply posting this so that it gets into the archive and may help other people. If any experts see anything wrong, please post a correction... 1. UML is great. Thanks to Jeff and BlaisorBlade and everyone else involved. 2. The site http://user-mode-linux.sourceforge.net is essential, but a lot of information is out of date and therefore either wrong for later kernels or just confusing. The following points list specific things in relation to this. Take what you read with a "grain of salt". 3. Recent kernels (from which version???) *do not* need a UML patch to compile and run as a guest. Briefly, "make ... ARCH=um" is the important part when compiling and kernel. 4. Recent kernels run SKAS0 by default, SKAS3 if the host kernel has support for it. The boot log *no longer* tells you what mode it is running. You can force "tt" mode if you want when you start the UML kernel: "mode=tt" option. 5. If you run certain distributions on your host, you may find it *very* hard or impossible to find a SKAS3 patch from http://www.user-mode-linux.org/~blaisorblade/patches/ that will patch the kernel to allow SKAS3 mode in your guests. For example, my host is Centos 4.4, which is a 2.6.9.who-knows-what-else kernel (i.e. Centos do back-ports from later kernels without updating the .9). I have tried almost every SKAS3 patch and cannot find any that will patch the kernel source. So, I'm running SKAS0, the default, for now... -- Best regards, Russell mailto:rus...@op... |
From: Blaisorblade <bla...@ya...> - 2007-03-02 00:05:48
|
On Thursday 01 March 2007 22:23, Russell Robinson wrote: > Hi, > > This is a list of what I've learned so far about UML. > > I'm simply posting this so that it gets into the archive and may help > other people. > > If any experts see anything wrong, please post a correction... > > 1. UML is great. Thanks to Jeff and BlaisorBlade and everyone > else involved. Thanks a lot, it is nice to see our work is useful to people. Working on it is fun, but knowing this helps doing the non-funny things. > 2. The site http://user-mode-linux.sourceforge.net is essential, but > a lot of information is out of date and therefore either wrong > for later kernels or just confusing. The following points list > specific things in relation to this. > Take what you read with a "grain of salt". > 3. Recent kernels (from which version???) *do not* need a UML patch Since 2.6.11 - the patch was merged in 2.6.9 but critical bugs existed. > to compile and run as a guest. Briefly, "make ... ARCH=um" > is the important part when compiling and kernel. > 4. Recent kernels run SKAS0 by default, SKAS3 if the host > kernel has support for it. The boot log *no longer* tells > you what mode it is running. Argh! It should - otherwise you're hitting a bug I guess. > You can force "tt" mode > if you want when you start the UML kernel: "mode=tt" option. I know no situation where it is recommended. Currently mode=tt cannot be compiled in and soon it will disappear from UML sources, I guess. > 5. If you run certain distributions on your host, you may find > it *very* hard or impossible to find a SKAS3 patch > from http://www.user-mode-linux.org/~blaisorblade/patches/ > that will patch the kernel to allow SKAS3 mode in your guests. > For example, my host is Centos 4.4, which is a > 2.6.9.who-knows-what-else kernel (i.e. Centos do back-ports > from later kernels without updating the .9). I have > tried almost every SKAS3 patch and cannot find > any that will patch the kernel source. > So, I'm running SKAS0, the default, for now... They are intended for vanilla kernels, and I think I've warned about this somewhere - and I'm always open about suggested improvements to it (since I know there is info but not always where it should). It is not difficult to port the SKAS patch to any given 2.6 kernel, it's just boring and time-consuming. -- Inform me of my mistakes, so I can add them to my list! Paolo Giarrusso, aka Blaisorblade http://www.user-mode-linux.org/~blaisorblade Chiacchiera con i tuoi amici in tempo reale! http://it.yahoo.com/mail_it/foot/*http://it.messenger.yahoo.com |
From: Russell R. <rus...@op...> - 2007-03-02 00:27:25
|
Hello Blaisorblade, Friday, March 2, 2007, 11:05:12 AM, you wrote: >> 5. If you run certain distributions on your host, you may find >> it *very* hard or impossible to find a SKAS3 patch >> from http://www.user-mode-linux.org/~blaisorblade/patches/ >> that will patch the kernel to allow SKAS3 mode in your guests. >> For example, my host is Centos 4.4, which is a >> 2.6.9.who-knows-what-else kernel (i.e. Centos do back-ports >> from later kernels without updating the .9). I have >> tried almost every SKAS3 patch and cannot find >> any that will patch the kernel source. >> So, I'm running SKAS0, the default, for now... B> They are intended for vanilla kernels, and I think I've warned about this B> somewhere - and I'm always open about suggested improvements to it (since I B> know there is info but not always where it should). B> It is not difficult to port the SKAS patch to any given 2.6 kernel, it's just B> boring and time-consuming. I'm quite keen to add the SKAS3 patch to my Centos 4.4 host kernel. I'd be happy to learn how to do it, and then write up a document about the process. My current guess about it would be this: 1. Find a later vanilla kernel. 2. Apply the appropriate SKAS patch to a copy of the kernel. 3. Diff the vanilla against the patched kernel. 4. Compare the changes, by eye, between the two files and get a programmer's understanding of the change. (Use "vi" or similar to view the whole context of the changes between the two files.) 5. Document the change. If there's any quicker way to understand the changes required, please let me know. -- Best regards, Russell mailto:rus...@op... |
From: Blaisorblade <bla...@ya...> - 2007-03-03 16:42:51
|
On Friday 02 March 2007 01:27, Russell Robinson wrote: > Hello Blaisorblade, > > Friday, March 2, 2007, 11:05:12 AM, you wrote: > >> 5. If you run certain distributions on your host, you may find > >> it *very* hard or impossible to find a SKAS3 patch > >> from http://www.user-mode-linux.org/~blaisorblade/patches/ > >> that will patch the kernel to allow SKAS3 mode in your guests. > >> For example, my host is Centos 4.4, which is a > >> 2.6.9.who-knows-what-else kernel (i.e. Centos do back-ports > >> from later kernels without updating the .9). I have > >> tried almost every SKAS3 patch and cannot find > >> any that will patch the kernel source. > >> So, I'm running SKAS0, the default, for now... > > B> They are intended for vanilla kernels, and I think I've warned about > this B> somewhere - and I'm always open about suggested improvements to it > (since I B> know there is info but not always where it should). > > B> It is not difficult to port the SKAS patch to any given 2.6 kernel, it's > just B> boring and time-consuming. > > I'm quite keen to add the SKAS3 patch to my Centos 4.4 host kernel. > > I'd be happy to learn how to do it, and then write up a document about > the process. If it's funny for you then welcome. Not for the faintheart though. > My current guess about it would be this: > 1. Find a later vanilla kernel. > 2. Apply the appropriate SKAS patch to a copy of the kernel. > 3. Diff the vanilla against the patched kernel. > 4. Compare the changes, by eye, between the two files and > get a programmer's understanding of the change. > (Use "vi" or similar to view the whole context of the changes > between the two files.) vimdiff is useful to compare two files, I use it often. > 5. Document the change. > If there's any quicker way to understand the changes required, please > let me know. The SKAS patch is not very huge, however it is tricky enough. Especially the SYSEMU related code - SKAS code is C only, while SYSEMU is tricky assembler code. To better understand the aim of the patch, probably the splitout version is worth a look - it is in the *-broken-out* tarballs (and use quilt to manage them, it is way useful!). Older patches were managed with Andrew Morton's patch-scripts, which was more error-prone however. This would allow you to backport bugfixes in -v8.2. One of them was a change intended to increase compatibility with Fedora/Redhat kernels, IIRC, while the other was a critical bugfix. -- Inform me of my mistakes, so I can add them to my list! Paolo Giarrusso, aka Blaisorblade http://www.user-mode-linux.org/~blaisorblade Chiacchiera con i tuoi amici in tempo reale! http://it.yahoo.com/mail_it/foot/*http://it.messenger.yahoo.com |