Re: [Xen-devel] Mmap to user space (question)

[Ruslan Nikolaev <nruslan_devel@xxxxxxxxx>]

--- On Wed, 10/6/10, Ruslan Nikolaev <nruslan_devel@xxxxxxxxx> wrote:

> From: Ruslan Nikolaev <nruslan_devel@xxxxxxxxx>
> Subject: Re: [Xen-devel] Mmap to user space (question)
> To: "Keir Fraser" <keir@xxxxxxx>
> Date: Wednesday, October 6, 2010, 9:53 PM
> 
> 
> --- On Wed, 10/6/10, Keir Fraser <keir@xxxxxxx>
> wrote:
> 
> > From: Keir Fraser <keir@xxxxxxx>
> > Subject: Re: [Xen-devel] Mmap to user space
> (question)
> > To: "Ruslan Nikolaev" <nruslan_devel@xxxxxxxxx>,
> xen-devel@xxxxxxxxxxxxxxxxxxx
> > Date: Wednesday, October 6, 2010, 10:52 AM
> > On 06/10/2010 00:10, "Ruslan
> > Nikolaev" <nruslan_devel@xxxxxxxxx>
> > wrote:
> > 
> > > Note: I already posted the message on xci-devel,
> but I
> > think this list is
> > > better suited for this question. So, I duplicated
> it
> > here.
> > > 
> > > ----
> > > 
> > > Hi
> > > 
> > > I need to map shared_info (provided by hypervisor
> to
> > each guest) to user space
> > > (read-only access). I am curious how I can do it,
> and
> > if there are some good
> > > examples for the case if NO autotranslation is
> > available. (BTW, Am I correct
> > > that I can use regular vm_insert_page or
> > remap_pfn_range if autotranslation is
> > > available?)
> > 
> > I wouldn't worry about auto-translate for PV guests.
> It's
> > pretty broken.
> > 
> > You will be using a similar mapping path to ioremap.
> So
> > something like
> > remap_pfn_range. A function called
> > xen_remap_domain_mfn_range sounds
> > promising. There's no grant table or other nonsense
> to
> > worry about. You just
> > need to get the page mapped into a special vmarea
> that
> > won't be subject to
> > paging or any other kernel VM machinery. Like mmap on
> > /dev/mem and
> > /proc/xen/privcmd, then.
> > 
> >  -- Keir
> 
> 
> 
> Thank you! I think, xen_remap_domain_mfn_range is indeed
> what I am looking for.
> 
> 
> Ruslan.
> 
> 
> > 
> > > If I am correct, shared_info page is mapped
> initially
> > into some fixmap area in
> > > the guest. However, no actual pfn exists for the
> page.
> > Instead, guest gets mfn
> > > address from start_info.
> > > 
> > > Now, what is the standard procedure to handle
> this
> > situation? I found
> > > xen_remap_domain_mfn_range function, but not sure
> if
> > it is what I am looking
> > > for. Also, I am not sure if I need to update
> grant
> > tables. I would greatly
> > > appreciate if someone can enlighten me on this
> issue,
> > and, perhaps, refer to
> > > some examples.
> > > 
> > > Thank you!
> > > 
> > > Ruslan.
> > > 
> > > 
> > > 
> > >       
> > > 
> > > _______________________________________________
> > > Xen-devel mailing list
> > > Xen-devel@xxxxxxxxxxxxxxxxxxx
> > > http://lists.xensource.com/xen-devel
> > 
> > 
> > 
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-devel
> > 
> 
> 
> 
> 




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