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

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."

(*) kind of a release/technical notes, an accompanying documentation for 
    update/release, where they can indicate the need of kernel commandline
    parameter to be added

Thanks,

-- 
Jiri Kosina
SUSE Labs