[POWERPC] merge iSeries i/o operations with the rest

David Woodhouse dwmw2 at infradead.org
Tue Sep 5 15:07:50 EST 2006

On Tue, 2006-09-05 at 12:08 +1000, Stephen Rothwell wrote:
> The low level i/o operations are now handled in iSeires by taking a
> trap when we access the (inaccessible) io memory region and calling
> the Hypervisor from the trap code.  

There was some discussion of the possibility of using the 'alternatives'
mechanism to patch the I/O instructions at run-time when we find we've
booted on iSeries -- just turning each one into a jump to a trampoline
which does the appropriate hypervisor calls, thus avoiding the overhead
of the trap each time.

Was that approach not viable, or not noticeably less of a performance
hit on iSeries?


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