linux-kernel - Re: [PATCH v2 02/17] powerpc/cell: Move data segment faulting code out of cell platform

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Date:	Thu, 02 Oct 2014 10:42:51 +1000
From:	Michael Neuling <mikey@...ling.org>
To:	Michael Ellerman <mpe@...erman.id.au>
Cc:	greg@...ah.com, arnd@...db.de, benh@...nel.crashing.org,
	anton@...ba.org, linux-kernel@...r.kernel.org,
	linuxppc-dev@...abs.org, jk@...abs.org, imunsie@...ibm.com,
	cbe-oss-dev@...ts.ozlabs.org,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Subject: Re: [PATCH v2 02/17] powerpc/cell: Move data segment faulting code
 out of cell platform

On Wed, 2014-10-01 at 16:47 +1000, Michael Ellerman wrote:
> On Tue, 2014-30-09 at 10:34:51 UTC, Michael Neuling wrote:
> > From: Ian Munsie <imunsie@....ibm.com>
> > 
> > __spu_trap_data_seg() currently contains code to determine the VSID and ESID
> > required for a particular EA and mm struct.
> > 
> > This code is generically useful for other co-processors.  This moves the code
> > of the cell platform so it can be used by other powerpc code.  It also adds 1TB
> > segment handling which Cell didn't have.
> 
> I'm not loving this.
> 
> For starters the name "copro_data_segment()" doesn't contain any verbs, and it
> doesn't tell me what it does.

Ok.

> If we give it a name that says what it does, we get copro_get_ea_esid_and_vsid().
> Or something equally ugly.

Ok

> And then in patch 10 you move the bulk of the logic into calculate_vsid().

That was intentional on my part.  I want this patch to be clear that
we're moving this code out of cell.  Then I wanted the optimisations to
be in a separate patch.  It does mean we touch the code twice in this
series, but I was hoping it would make it easier to review.  Alas. :-)

> So instead can we:
>  - add a small helper that does the esid calculation, eg. calculate_esid() ?
>  - factor out the vsid logic into a helper, calculate_vsid() ?
>  - rework the spu code to use those, dropping __spu_trap_data_seg()
>  - use the helpers in the cxl code

OK, I think I can do that.  I might change the name to something better
in this patch, but I'll leave these cleanups to the later patch 10.

Mikey

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