>
> On Tue, Nov 13, 2012 at 10:24 AM, Daniel De Graaf <
dgdegra@xxxxxxxxxxxxx>wrote:
>
>> 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)
>>>>
>>>>>
>>>
