Re: use xs_watch from userspace and use epoll instead of select

[Vasiliy G Tolstov <v.tolstov@selfip.ru>]

On Mon, 2011-06-06 at 12:00 +0100, Ian Campbell wrote:
> On Mon, 2011-06-06 at 11:05 +0100, Vasiliy G Tolstov wrote:
> > On Mon, 2011-06-06 at 10:48 +0100, Ian Campbell wrote:
> 
> > > What are you actually trying to build?
> 
> > I'm try to build daemon, that can recieve command via xenstore (xs_watch
> > for specific path), via /dev/hvcN (serial char interface), now i'm try
> > to use gntmem mechanism to do this too. If one method not available or
> > not work or some errors accured - i'm try next. 
> > /dev/hvcN Not good sometimes, becouse in some domU i have gentty on this
> > port.
> > xenstore - has limit in size of message...
> 
> Interesting.
> 
> > In kernel side xen thing more easy to understand. Use it under userspace
> > need deep googling =).
> 
> I'm afraid so.
> 
> Remember that the underlying grant table hypercall's and mechanisms are
> the same in both kernel and userspace and the APIs provided reflect that
> -- userspace is not all that different.
> 
> In userspace you might need (actually I think it's probably required)
> to use the gntalloc driver (added to pvops by Daniel de Graff around
> 2.6.39 I think) to get memory suitable for granting out.
> 
> > Ok if i use grant pages mechanism - do i have notify for new message
> > after it arrives? If i use xs from domU i need libxc under it insted of
> > libxenstore ?
> 
> Yes you need to notify, libxc provides an interface to event channels as
> well as grant tables.
> 
> You will probably need both libxc and libxenstore. You use xenstore to
> negotiated the event channel and shared page with your peer and libxc to
> create, map, signal them etc.
> 
> Ian.
> 
> 

Thanks for suggestions. I'm try investigate e-mail list with gntdev
patches and write example code..
-- 
Vasiliy G Tolstov <v.tolstov@selfip.ru>
Selfip.Ru