[MODERATED] Re: ***UNCHECKED*** Re: [PATCH v5 08/11] TAAv5 8

On Mon 14-10-19 21:51:42, speck for Jiri Kosina wrote:
> On Mon, 14 Oct 2019, speck for Thomas Gleixner wrote:
> 
> > The real question is whether machines on which SAP/HANA runs are just 
> > random boxes/VMs which would be affected by the 'update and reboot 
> > world' treatment or whether SAP/HANA runs on dedicated systems which are 
> > carefully administrated by sysadmins with brains turned on.
> > 
> > If it's the random box affected by 'update and reboot world' then disabling
> > TSX by default is obviously going to be a source of regressions and we have
> > to bite the bullet.
> > 
> > If not, then the sysadmins will anyway do some very careful evaluation 
> > and checking, read documentation and add 'WE_REALLY_WANT_TSX' on the 
> > kernel command line. In that case I rather disgruntle a few sysadmins 
> > and gain a useful setup for everyone else.
> 
> [ if this archive is ever going to be published, please remove this mail 
>   from it, thanks ]
> 
> So we talked to SAP about exactly this, and they expressed a real worry 
> along the lines of (just my paraphrase, not really verbatim quote of 
> anybody):
> 
> 	"of course we will put it into a SAP note (*), but realistically, 
> 	not everybody (by far) is reading those. If this regressess on a 
> 	handful of platforms, we (together with the OS vendor) could 
> 	probably handle the followup reports, but if it happens all across 
> 	the board, it'd surely be overwhelming, to put it mildly. It'll"
> 	basically promptly escalate to a support disaster."

And I would just give my personal experience. We have been through many
bug reports where it simply turned out that a long deprecated (by a SAP
note) configuration has been still in place because that is what was
done at the time of deployment and never changed since.
-- 
Michal Hocko
SUSE Labs