Re: [Xen-devel] [RFC PATCH 11/24] ARM: vGICv3: handle virtual LPI pending and property tables

[Julien Grall <julien.grall@xxxxxxx>]

Hi Stefano,

On 02/11/16 17:41, Stefano Stabellini wrote:
> On Wed, 2 Nov 2016, Julien Grall wrote:
> > > +    }
> > > +
> > > +    ptr = vmap(pages, nr_pages);
> > I am not a big fan of the vmap solution for various reasons:
> >         - the VMAP area is small (only 1GB) it will not scale (you seem
> > to use it to map pretty much all memory provisioned for the ITS)
> >         - writing in a register cannot fail, how do you co-op with that?
> >
> > I think the best approach here is to use a similar approach as
> > copy_*_guests helpers but dealing with IPA rather than guest VA.
> I don't like the idea of using the vmap for this either, but the problem
> with the copy_*_guest approach is that it only maps one page at a time.
> It is unable to map multiple pages contiguously, which seems to be
> required here.
We will get into trouble very quickly with the vmap solution. The memory 
provisioned by the ITS can be quite big. Each GITS_BASER can hold up to 
16MB (if I computed correctly) of memory.
The question is why do we need to map the page contiguously? Can we do 
in a different way?
Regards,

--
Julien Grall

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