ioremap of pci region on pSeries LPAR vs SMP

Linas Vepstas linas at
Wed Jan 12 09:17:23 EST 2005

On Tue, Jan 11, 2005 at 11:08:45AM +1100, Anton Blanchard was heard to remark:
> Ive seen HPC stuff that wants to be able to mmap a PCI cards resources into
> userspace. Their hack on ppc64 was to look at the high nibble of the
> address and convert it to a non EEH address if required :)
> Im not sure how best to solve the userspace mmap issue but there are a
> few groups wanting that.

Somewhat off-topic ... but ...

1) If you design your hardware correctly, there are some amazing things
   you can do (performance wise) by mmaping pci card resources into user
   space.  If your hardwares is done right, then user corruption can't 
   hurt the system. This was the defacto method for getting high 
   performance graphics on IBM RS/6000, sgi, HP and Sun workstations 
   many moons ago.

2) There is interest in the virtual i/o community about mmaping 
   funky stuff to userspace, but that conversation may be for a 
   different day.  The question is (for example) how to build
   a high-performance virtual scsi server in userspace (without
   kernel pieces) which is a design point some people like.


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