Re: [Xen-devel] [PATCH v2] xen/arm: Switch OMAP5 secondary cores into hyp mode

[Julien Grall <julien.grall@xxxxxxx>]

Hi Denis,

On 17/07/2019 17:32, Denis Obrezkov wrote:
> > I am trying to understand how this ever worked. omap5_smp_init is called
> > by two sets of platforms (based on compatible):
> >     - ti,dra7: there were some hacks in U-boot to avoid the SMC. If I am
> > right, then I would not bother to support hacked U-boot.
> >     - ti,omap5: [1] suggest that U-boot do the switch for us but it is
> > not clear whether this is upstreamed. @Chen, I know you did the port a
> > long time ago. Do you recall how this worked?
> >
> > Linux seems to use the smc on any dra7 and omap54xx. So maybe we can use
> > safely here.
> > I don't understand your concerns to the full extent. What should be
> investigated?
Well, Xen has been supported the omap5 for quite a while. So there are two 
possibilities regarding the current SMP code:
   1) It is totally broken and therefore never worked on any omap5 platform.
   2) It works but with maybe modification in U-boot.

Looking at the mailing list archive and wiki, I believe 2) is closer to the 
current reality. So this raise the question whether your patch will break any 
existing setup.
Don't get me wrong, the code is perfectly fine as, to the best of my knowledge, 
it matches what Linux does. However, I would like to see an analysis written in 
the commit message regarding what's going to happen for any existing setup.
Cheers,

--
Julien Grall

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