Re: [PATCH 4/5] arm64: Verify CPU errata work arounds on hotplugged CPU

[Suzuki K Poulose]

On 15/04/16 15:12, Will Deacon wrote:
> On Fri, Apr 15, 2016 at 03:10:27PM +0100, Suzuki K Poulose wrote:
> > On 14/04/16 18:49, Suzuki K Poulose wrote:
> > > On 14/04/16 18:39, Will Deacon wrote:
> > > > On Wed, Apr 06, 2016 at 12:24:13PM +0100, Suzuki K Poulose wrote:
> > > > > CPU Errata work arounds are detected and applied to the
> > > > > kernel code at boot time and the data is then freed up.
> > > > > If a new hotplugged CPU requires a work around which
> > > > > was not applied at boot time, there is nothing we can
> > > > > do but simply fail the booting.
> > > >
> > > > Hmm, wouldn't it be better not to free the alternative text for errata
> > > > workarounds instead?
> > >
> > > We could. I don't have a strong opinion. If there are no objections, I could
> > > adopt it.
> >
> > The alternatives have been merged to .init by :
> >
> > commit 9aa4ec1571da6236 ("arm64: mm: fold alternatives into .init")
> >
> > Mark,
> >
> > Do you have any concerns on applying alternatives for CPUs turned online later ?
> > We have to revert the patch above to get going
>
> Well, note that I'm only suggesting that we keep the alternatives for
> CPU errata workarounds.

So to confirmt, do you mean for now we could do :

 - Not release the alternatives for errata work arounds.
 - And retain the check for new erratas, failing the CPUs.

And in a follow up series,

 - Add support for applying errata work arounds later, as we find
   a new CPU which requires it
 - and remove the constraint above ?


Suzuki