Re: [Xen-devel] [PATCH 02/11] xen/arm: vpl011: Add new hvm params in Xen for ring buffer/event setup

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Fri, 14 Apr 2017, Bhupinder Thakur wrote:
> Hi Stefano,
> 
> On 12 April 2017 at 03:37, Stefano Stabellini <sstabellini@xxxxxxxxxx> wrote:
> > On Tue, 11 Apr 2017, Bhupinder Thakur wrote:
> >> Hi,
> >>
> >> Kindly let me know if my understanding is correct.
> >>
> >> Using a domctl API will allow us to keep the vUART configuration
> >> flexible. Currently, we can operate on one ring-buf PFN and an event
> >> channel port only for a single vUART but if we use DOMCTL interface,
> >> then we can effectively get/set multiple event channel ports/multiple
> >> PFNs from/to Xen in a single domctl call.
> >>
> >> I am not clear who will be the caller of this domctl API. Is it
> >> xenconsoled or the toolstack? Currently, xenconsoled reads the
> >> ring-buf PFN and event channel from the xenstore, which is populated
> >> by the toolstack.
> >
> > The caller could be either, but I think it would make sense for it to be
> > xenconsoled to cut the middle-man (xl).
> >
> I see the issue with Xenconsoled getting the PFN using a DOMCTL API.
> 
> PFN is allocated in alloc_magic_pages() which is part of
> libxenguest.so and the DOMCTL API is part of libxenctrl.so. As per my
> understanding, libxenguest.so has dependency on libxenctrl.so but not
> the other way round.So I am not sure how libxenctrl can call into
> libxenguest to get the PFN.
> 
> If the DOMCTL API is called from libxenguest then I can get the PFN easily.

Yes, that is the case. libxenguest would call libxenctrl to issue
domctls. You would simply replace hvm_param reads/writes with a new pair
of domctl, conceptually very similar.

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel