Re: [Xen-devel] Proposal to allow setting up shared memory areas between VMs from xl config file

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 15.05.17 at 16:13, <julien.grall@xxxxxxx> wrote:
> On 15/05/17 13:28, Jan Beulich wrote:
>>>>> On 15.05.17 at 12:21, <julien.grall@xxxxxxx> wrote:
>>> On Zhongze proposal, the share page will be mapped at the a specific
>>> address in the guest memory. I agree this will require some work in the
>>> toolstack, on the hypervisor side we could re-use the foreign mapping
>>> API. But on the guest side there are nothing to do Xen specific.
>>
>> So what is the equivalent of the shared page on bare hardware?

No answer here?

>>> What's the benefit? Baremetal guest are usually tiny, you could use the
>>> device-tree (and hence generic way) to present the share page for
>>> communicating. This means no Xen PV drivers, and therefore easier to
>>> move an OS in Xen VM.
>>
>> Is this intended to be an ARM-specific extension, or a generic one?
>> There's no DT on x86 to pass such information, and I can't easily
>> see alternatives there. Also the consumer of the shared page info
>> is still a PV component of the guest. You simply can't have an
>> entirely unmodified guest which at the same time is Xen (or
>> whatever other component sits at the other end of the shared
>> page) aware.
> 
> The toolstack will setup the shared page in both the producer and 
> consumer guest. This will be setup during the domain creation. My 
> understanding is it will not be possible to share page after the two 
> domains have been created.

Whether this is going to become too limiting remains to be seen, but
in any event this doesn't answer my question regarding the x86 side.

Jan


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