[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Immediate kernel panic using gntdev device
On 11/12/2012 08:15 AM, D Sundstrom wrote: > Thank you Pablo. > > It makes no difference if I run both the src-add and map from the same > domain or from different DomU domains. > Whichever DomU I run the map function in crashes immediately. Mapping your own grants (which is what the test run you showed did) might cause problems - although it's a bug that needs to be fixed, if so. You may want to try using the vchan-node2 tool (tools/libvchan) for testing and as an example user. > You mention Dom0. I just want to be clear that I'd like to share > between two DomU domains. Have you gotten this to work? That was the goal of gntalloc/libvchan - it should work (and has for me). > I also tried the userspace APIs provided by Xen such as > xc_gnttab_map_grant_ref() and these also crash. Of course, these use > the same driver IOCTLs, so this isn't a surprise. > > I'll need to see if I can get some debug info from the DomU kernel to > make progress. You might want to try booting your domU with console=hvc0 and look at xl console - that will usually give you useful backtraces. Without that, it's rather difficult to tell what the problem is. > If I can get this to work, are there any restrictions on sharing large > amounts of memory? Say 160Mb? Or are grant tables intended for a > small number of pages? There are restrictions within the modules (default is 1024 4K pages), and in Xen itself for the number of grant table and maptrack pages - but I think those can be adjusted via a boot parameter. The grant tables aren't currently intended to share large amounts of memory, so you may run in to some inefficiencies when doing the map/unmap. If you're using an IOMMU for one of the domUs, this may end up being especially costly. > Thanks, > David > > > > On Mon, Nov 12, 2012 at 5:36 AM, Pablo Llopis <pllopis@xxxxxxxxxxxxxxxxx> > wrote: >> >> It is not clear from your output from which domain you are running >> each command. It looks like you are trying to issue a grant and map it >> from within the same domain. That's probably the reason it crashes. >> You are supposed to run this tool from both domains, running the calls >> which interface with gntalloc from one domain, and the calls which >> interface with gntdev from the other domain. >> In any case, the domid you have to specify in the map must be the >> domid of the domain which issued the grant. In other words, when >> creating a grant, the domid which is granted access is specified. When >> mapping a grant, the domid which issued the grant is specified. (i.e. >> If you did "src-add 8" from dom0 you should run map 0 1372 from domU >> 8) >> >>> > > _______________________________________________ > Xen-devel mailing list > Xen-devel@xxxxxxxxxxxxx > http://lists.xen.org/xen-devel > -- Daniel De Graaf National Security Agency _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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