[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Problem Reading from XenStore in DomU
On Mon, May 16, 2016 at 12:11 PM, Dagaen Golomb <dgolomb@xxxxxxxxxxxxxx> wrote: > On Mon, May 16, 2016 at 12:03 PM, Dagaen Golomb <dgolomb@xxxxxxxxxxxxxx> > wrote: >> On Mon, May 16, 2016 at 11:55 AM, Doug Goldstein <cardoe@xxxxxxxxxx> wrote: >>> On 5/15/16 8:41 PM, Dagaen Golomb wrote: >>>>> On 5/15/16 8:28 PM, Dagaen Golomb wrote: >>>>>>> On 5/15/16 11:40 AM, Dagaen Golomb wrote: >>>>>>>> Hi All, >>>>>>>> >>>>>>>> I'm having an interesting issue. I am working on a project that >>>>>>>> requires me to share memory between dom0 and domUs. I have this >>>>>>>> successfully working using the grant table and the XenStore to >>>>>>>> communicate grefs. >>>>>>>> >>>>>>>> My issue is this. I have one domU running Ubuntu 12.04 with a default >>>>>>>> 3.8.x kernel that has no issue reading or writing from the XenStore. >>>>>>>> My work also requires some kernel modifications, and we have made >>>>>>>> these changes in the 4.1.0 kernel. In particular, we've only added a >>>>>>>> simple hypercall. This modified kernel is what dom0 is running, on top >>>>>>>> of Xen 4.7 rc1. >>>>>>> >>>>>>> Without reading the rest of the thread but seeing the kernel versions. >>>>>>> Can you check how you're communicating to xenstore? Is it via >>>>>>> /dev/xen/xenbus or /proc/xen/xenbus? Anything after 3.14 will give you >>>>>>> deadlocks if you try to use /proc/xen/xenbus. Xen 4.6 and newer should >>>>>>> prefer /dev/xen/xenbus. Same thing can happen with privcmd but making >>>>>>> that default didn't land until Xen 4.7. Since you're on the right >>>>>>> versions I expect you're using /dev/xen/xenbus but you never know. >>>>>> >>>>>> How do I know which is being used? /dev/xen/xenbus is there and so is >>>>>> process/xen/xenbus. Could this be a problem with header version >>>>>> mismatches or something similar? I'm using the xen/xenstore.h header >>>>>> file for all of my xenstore interactions. I'm running Xen 4.7 so it >>>>>> should be in /dev/, and the old kernel is before 3.14 but the new one >>>>>> is after, but I would presume the standard headers are updated to >>>>>> account for this. Is there an easy way to check for this? Also, would >>>>>> the same issue cause writes to fails? Because writes from the same >>>>>> domain work fine, and appear to other domains using xenstore-ls. >>>>>> >>>>>> Regards, >>>>>> Dagaen Golomb >>>>>> >>>>> >>>>> Use strace on the process and see what gets opened. >>>> >>>> Ah, of course. It seems both the working and non-working domains are >>>> using /proc/... >>>> >>>> Regards, >>>> Dagaen Golomb >>>> >>> >>> >>> How are you starting them? Can you confirm its attempting /dev/ first? >>> Xen 4.7 should prefer /dev/. For all kernels in my domU, without setting any environment variables they use /proc/. For 4.1.0 this did not work, but works with /dev/ when using environment variable. Is this supposed to try /dev/ before /proc/? Because this doesn't appear the case according to strace. I think this is a bug. Regards, Dagaen Golomb _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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