Re: kernel unaligned accesses on IA64 in IDE

[Nishanth Aravamudan <nacc@us.ibm.com>]

On 22.08.2008 [16:15:22 -0500], James Bottomley wrote:
> On Fri, 2008-08-22 at 13:36 -0700, Luck, Tony wrote:
> > > How about long instead of int.  int leaves us with the possibility that
> > > something else will expect 8 byte alignment.
> > 
> > How about this?
> > 
> > Align __cmd to ward off kernel unaligned access consoles messages on
> > ia64 (and perhaps make an almost imperceptible performance improvement
> > on other architectures that can handle unaligned access, but do so
> > more slowly than aligned accesses).
> > 
> > Signed-off-by: Tony Luck <tony.luck@intel.com>
> 
> Yuk, really ... you're blowing out the size of a critical structure by
> padding which is unnecessary in 99% of cases.  Commands are supposed to
> be byte streams. Adding extra alignment to generic code because some
> driver has strange rules isn't very well layered.
> 
> Also, these are string out instructions ... They don't have any
> alignment requirements (or they're not supposed to; they're like
> memcpy); they're modelled on the x86 instructions
> 
> What about this as the obvious solution?  It makes the ia64 version of
> this command behave exactly as the x86 version does.
> 
> James

Tested-by: Nishanth Aravamudan <nacc@us.ibm.com>

Thanks,
Nish

-- 
Nishanth Aravamudan <nacc@us.ibm.com>
IBM Linux Technology Center