[Xen-devel] Re: [patch 06/26] Xen-paravirt_ops: paravirt_ops: allocate a fixmap slot

[Ingo Molnar <mingo@xxxxxxx>]

* Jeremy Fitzhardinge <jeremy@xxxxxxxx> wrote:

> > Yes.  vmalloc would have the annoying side-effect of actually 
> > allocating some pages which would be shadowed by the remapping, but 
> > I guess get_vm_area would do the job.  I'll give it a go.
> 
> Hm, this is a bit awkward.  We need to map the shared info page fairly 
> early - say, around paging_init - but we're still on the bootmem 
> allocator at that point, so get_vm_area isn't usable yet.  Using a 
> fixmap keeps things simple.  It seems to me that having a single 
> fixmap available is useful for this kind of simple/early mapping, and 
> if someone needs to map something larger, then they can put it off 
> until get_vm_area() is available...

fair enough. Please rename it to FIX_PARAVIRT_BOOTUP - you can still 
rely on it being available later on too, but we'd like to give everyone 
the right fundamental idea about this: it's meant to be a limited, 
inflexible interface for bootstrap only.

        Ingo

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