Hi, I have another question about memory sharing among domains(domUs). I know that grant table can be used for memory sharing. But my question is if it is possible to setup memory sharing before domain starts. For example, suppose I have 2 domUs: A and B. Before A and B are booted, is it possible to map certain physical pages of A and B into the same machine pages? Any comment? (btw, an unrelated question, if I do printk in Xen HVM, what''s an easy way to read that message?) Thanks Haifeng _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
On Tue, 2007-11-20 at 20:26 -0700, Haifeng He wrote:> Hi, > > I have another question about memory sharing among domains(domUs). I know that > grant table can be used for memory sharing. But my question is if it is possible > to setup memory sharing before domain starts. For example, suppose > I have 2 domUs: A and B. Before A and B are booted, is it possible to map > certain physical pages of A and B into the same machine pages? Any comment?yes, this is possible. quite a number of pages get ''shared'' that way, e.g. the console and xenstore mfns. see e.g. the definition of the start_info struct in the xen headers and see e.g. the domain builder code (tools/libxc/xc_(linux|*)_build.c) on how this is set up from dom0. you might just need to add a few lines to get what you want. 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 11/20/07, Daniel Stodden <stodden@cs.tum.edu> wrote:> > On Tue, 2007-11-20 at 20:26 -0700, Haifeng He wrote: > > Hi, > > > > I have another question about memory sharing among domains(domUs). I know > that > > grant table can be used for memory sharing. But my question is if it is > possible > > to setup memory sharing before domain starts. For example, suppose > > I have 2 domUs: A and B. Before A and B are booted, is it possible to map > > certain physical pages of A and B into the same machine pages? Any > comment? > > yes, this is possible. quite a number of pages get ''shared'' that way, > e.g. the console and xenstore mfns. see e.g. the definition of the > start_info struct in the xen headers and see e.g. the domain builder > code (tools/libxc/xc_(linux|*)_build.c) on how this is set up from dom0. > you might just need to add a few lines to get what you want. >Thank you for your reply. I checked the above code. If I understand correctly, the page sharing of console and xenstore is between dom0 and domU instead of between domUs. Secondly, the mapping is one to one, i.e., one mfn page allocated to domU is mapped to dom0. However, what I am looking for is, probably one to many mapping. That is, one mfn page can be mapped into physical page in multiple domUs and shared by them. Any idea? Thanks Haifeng> 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 21/11/07 04:45, "Haifeng He" <hehaifeng2nd@gmail.com> wrote:> Thank you for your reply. I checked the above code. > If I understand correctly, the page sharing of console and xenstore is > between dom0 and domU instead of between domUs. Secondly, > the mapping is one to one, i.e., one mfn page allocated to domU > is mapped to dom0. However, what I am looking for is, probably one to many > mapping. That is, one mfn page can be mapped into physical page in > multiple domUs and shared by them. Any idea?This isn''t currently possible. -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
On 21/11/07 03:26, "Haifeng He" <hehaifeng2nd@gmail.com> wrote:> (btw, an unrelated question, if I do printk in Xen HVM, what''s an easy > way to read that message?)Write bytes to I/O port 0xe9 and lines of output will appear on Xen''s emergency console (e.g., serial line) if you set guest_loglvl=all. -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
On Nov 21, 2007 12:56 AM, Keir Fraser <Keir.Fraser@cl.cam.ac.uk> wrote:> On 21/11/07 04:45, "Haifeng He" <hehaifeng2nd@gmail.com> wrote: > > > Thank you for your reply. I checked the above code. > > If I understand correctly, the page sharing of console and xenstore is > > between dom0 and domU instead of between domUs. Secondly, > > the mapping is one to one, i.e., one mfn page allocated to domU > > is mapped to dom0. However, what I am looking for is, probably one to many > > mapping. That is, one mfn page can be mapped into physical page in > > multiple domUs and shared by them. Any idea? > > This isn''t currently possible. >But is there a way to do it by modifying the Xen source? For example, during domain creation, is it possible to let Xen assign certain mfn pages to particular physical pages in the new domain? ( I have been trying to figure out how Xen assign mfn pages to new domain but still not very successful. The code looks quite complicated.) Thanks Haifeng> -- Keir > > >_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel