Re: [Xen-devel] Immediate kernel panic using gntdev device

[D Sundstrom <sunds@xxxxxxxxxx>]

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.

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?

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.

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?

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)
>
> >

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