Re: Fwd: [Xen-devel] Inter-domain shared memory facility in Xen?

[Daniel Stodden <dns@xxxxxxxxxxxx>]

On Thu, 2007-11-01 at 09:40 -0400, David Stone wrote:

> Thanks for your help on this.  So based on your responses I just want
> to confirm my understanding is correct...is it true that:
> 
> 1. It is currently possible to establish shared memory between Dom0
> and DomU, but
> 2. It is currently not possible to establish shared memory between two
> DomUs in an released Xen versions, nor the current xen-unstable branch
> nor any other branch on http://xenbits.xensource.org.  There are
> projects that address this that you mentioned though.

i did not follow this discussion until now, but are you aware of the
grant table facility part of the PV interface?

xensocket and xway are projects targeting sockets-based APIs. grant
table ops are, like all hypercalls, a kernel-level interface, but the
xen-specific modules in dom0 as well as the control libraries already
contain some code to let userland use it.

regarding item 2.: no, shared memory can be established between
arbitrary domains. otherwise, the sockets interfaces could not work,
right? grants work about as follows: dom1 'grants' a page to dom2, which
creates a 'grant reference'. that grant reference can be used by dom2 to
(map|transfer) that page into its respective own address space(s). 

this is what e.g. the pv driver codebase is using for bulk data
transfers. similarly, a userland interface may be built to e.g.
implement something similar to posix shm on top of it. if that is what
you need.

not sure what exactly you're looking for, though.

grant refs are concisely described in the interface manual.

regards,
dns

-- 
dns@xxxxxxxxxxxx

Wire up your home and stay there.




_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel