svn commit: r286787 - head/sys/x86/x86

[Konstantin Belousov]

On Sun, Aug 16, 2015 at 10:16:53AM +0200, Roger Pau Monn?? wrote:
> pmap_map_io_transient contains some of this logic, but it uses
> vmem_alloc (with M_WAITOK) instead of a pcpu pageframe, which defeats
> part of the purpose of this change and cannot be used as-is.

This logic can be repeated, but it is probably too much for the purpose.
It would be enough to have single frame (we cannot reuse CMAP1),
protected by a spin mutex.  I do not see much sense in providing
optimized per-cpu frames for this case.