Re: CVS commit: src/sys/arch

[Thor Lancelot Simon <tls%panix.com@localhost>]

On Sun, Jul 08, 2018 at 04:49:51PM +0200, Kamil Rytarowski wrote:
> On 08.07.2018 12:01, Martin Husemann wrote:
> > 
> > This is unecessary churn for no good reason, please stop it.
> > 
> > But worse are the other changes you are doing where kubsan insists on
> > natural alignement for {u,}int_{16,32,64} types, which is plain wrong,
> > these CPUs do not require that alignment (and it is not even clear
> > if kubsan propagates the alignment of structures correctly).
> > 
> > Martin
> > 
> 
> I've started a thread on it in tech-kern@. Please move the discussion there.

OK, let's talk about it here.  I would suggest that making changes to
MD code to conform to alignment constraints not actually present on the
"M" in question is not the right thing to do.  I'd further suggest that
there are in fact cases where it can break things or harm performance
(the trick conditionally used in some device drivers of intentionally
misaligning structures so their fields accessed by DMA meet DMA alignment
constraints comes to mind).

-- 
  Thor Lancelot Simon	                                     tls%panix.com@localhost
 "The two most common variations translate as follows:
	illegitimi non carborundum = the unlawful are not silicon carbide
	illegitimis non carborundum = the unlawful don't have silicon carbide."