From: Dagaen Golomb <dgolomb@seas.upenn.edu>
To: Doug Goldstein <cardoe@cardoe.com>
Cc: xen-devel@lists.xen.org
Subject: Re: Problem Reading from XenStore in DomU
Date: Sun, 15 May 2016 21:41:10 -0400 [thread overview]
Message-ID: <CALcuvTiX4DAM7myPXFsoO_JTP1n0eFvDU4iwFmuGC9GzTgnuKQ@mail.gmail.com> (raw)
In-Reply-To: <242b1768-e958-0752-a6c2-8ac1a68468aa@cardoe.com>
> 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
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next prev parent reply other threads:[~2016-05-16 1:41 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-15 16:40 Problem Reading from XenStore in DomU Dagaen Golomb
2016-05-15 17:04 ` Andrew Cooper
2016-05-15 19:54 ` Dagaen Golomb
2016-05-15 19:59 ` Dagaen Golomb
2016-05-15 20:35 ` Meng Xu
2016-05-15 21:11 ` Dagaen Golomb
2016-05-15 23:47 ` Dagaen Golomb
2016-05-16 1:21 ` Doug Goldstein
2016-05-16 1:28 ` Dagaen Golomb
2016-05-16 1:31 ` Doug Goldstein
2016-05-16 1:41 ` Dagaen Golomb [this message]
2016-05-16 3:15 ` Meng Xu
[not found] ` <CALcuvTjPpPQs5=i5uWvO2x_Krm-3j7u867yw4y1iWDNV7J83NA@mail.gmail.com>
[not found] ` <CALcuvTjfh4J8y0B_4GaajcgYQKvUJA3VFBrLFSq0HOVdWSyf0w@mail.gmail.com>
2016-05-16 3:30 ` Dagaen Golomb
2016-05-16 3:57 ` Meng Xu
2016-05-16 9:52 ` Andrew Cooper
2016-05-16 13:12 ` Jonathan Creekmore
2016-05-16 13:16 ` Dagaen Golomb
2016-05-16 15:55 ` Doug Goldstein
2016-05-16 16:03 ` Dagaen Golomb
2016-05-16 16:11 ` Dagaen Golomb
2016-05-16 16:20 ` Dagaen Golomb
2016-05-16 19:12 ` Doug Goldstein
2016-05-16 19:52 ` Dagaen Golomb
2016-05-16 19:56 ` Dagaen Golomb
2016-05-16 20:18 ` Dagaen Golomb
2016-05-16 22:25 ` Doug Goldstein
2016-05-16 22:29 ` Dagaen Golomb
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