On Wed, 11 May 2016 13:09:45 -0400, Tony Harminc wrote:
>
>The biggest reason to use VIO rather than the various alternatives
>mentioned is that it is compatible. An existing application need know
>nothing about it, and can be offered improved performance with no code
>changes. In these days of large memory it may seem quaint, but it has
>its place.
> 
Compatible.  I recall a time when IEBCOPY couldn't deal with VIO because
IEBCOPY used EXCP V=R, but VIO relying on paging could accept only
virtual addresses.  (Surprisingly?) this was addressed in VIO (by a sort
of reverse LRA/DAT?) rather than modifying IEBCOPY.  I wonder what the
cost, and whether nowadays IEBCOPY eschews EXCP V=R so it may run
with AC=0.

-- gil

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