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Re: [Xen-devel] Problem Reading from XenStore in DomU

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.

Doug Goldstein

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