kern/48754: ahcisata hardware alignement requirements not guaranteed by driver

[martin%NetBSD.org@localhost]

>Number:         48754
>Category:       kern
>Synopsis:       ahcisata hardware alignement requirements not guaranteed by 
>driver
>Confidential:   no
>Severity:       critical
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Apr 18 06:20:00 +0000 2014
>Originator:     Martin Husemann
>Release:        NetBSD 6.99.40
>Organization:
The NetBSD foundation, Inc.
>Environment:
System: NetBSD night-owl.duskware.de 6.99.40 NetBSD 6.99.40 (NIGHT-OWL) #248: 
Fri Apr 18 07:41:17 CEST 2014 
martin%night-owl.duskware.de@localhost:/usr/src/sys/arch/amd64/compile/NIGHT-OWL
 amd64
Architecture: x86_64
Machine: amd64
>Description:
As discussed in PR kern/48550 we may call the ahcisata driver with misaligned
target buffers. The case in that PR has been worked around, but in general
the backend drivers should be able to deal with this.

The hardware seems to require 2-byte alignement of buffers.

>How-To-Repeat:
Pass an unaligned target buffer to ahcisata and run a command, watch results
being delivered at buffer address & ~2UL.

>Fix:
Use bounce buffers in this case?