Re: [Xen-users] Grant Table Access By Multiple Domains

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Tue, 22 Mar 2016, Dagaen Golomb wrote:

> Hello,
> 
> I have written two user-space applications. One gets a grant from Xen
> and writes some data to a page. The other maps the page and reads the
> data. I am using the userspace grant table mechanism
> (gntalloc/gntdev).
> 
> They work perfectly for transfers between two domains. However, I
> would like to set up a global memory page, where multiple guests can
> all simultaneously map the same page. Right now, it appears I can only
> pass in one domid when using gntalloc, and when I change the domain
> and issue the IOCTL again this results in a separate grant (and I
> presume, page). This makes sense since they are logically two
> different grant requests.
> 
> Is there a way I can allow more than one domain to map the same
> granted page? For example, Instead of granting a page to just domid 1,
> I'd like to say domid's 1, 2, and 3 can all map it simultaneously.
> Thanks for any help and insight.

No, AFAIK you will have to create several grants in order to give 
permissions to different domains. Grants are a way to share memory between 
2 domains (so it's a 1:1 sharing), but not amongst multiple domains (1:N).

Roger.

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