linux-kernel - Re: CXL: Fix PSL error due to duplicate segment table entries

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Message-Id: <1414455360-sup-2142@delenn.ozlabs.ibm.com>
Date:	Tue, 28 Oct 2014 11:17:47 +1100
From:	Ian Munsie <imunsie@....ibm.com>
To:	Michael Ellerman <mpe@...erman.id.au>
Cc:	cbe-oss-dev <cbe-oss-dev@...ts.ozlabs.org>,
	mikey <mikey@...ling.org>, arnd <arnd@...db.de>,
	jk <jk@...abs.org>, greg <greg@...ah.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linuxppc-dev <linuxppc-dev@...abs.org>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	anton <anton@...ba.org>
Subject: Re: CXL: Fix PSL error due to duplicate segment table entries

Excerpts from Michael Ellerman's message of 2014-10-27 17:41:00 +1100:
> On Mon, 2014-27-10 at 04:24:35 UTC, Ian Munsie wrote:
> > From: Ian Munsie <imunsie@....ibm.com>
> > 
> > In certain circumstances the PSL can send an interrupt for a segment
> 
> Define PSL before using it please.

ok

> > The CXL driver did not expect this situation and did not check if a
> 
> does not and does not, you haven't patched it yet.

ok

> > Some of the code has been refactored to simplify it - the segment table
> > hash has been moved from cxl_load_segment to find_free_sste where it is
> 
> Any reason that's not a separate patch?

ok, I'll split it.

> > used and we have disabled the secondary hash in the segment table to
> > reduce the number of entries that need to be tested from 16 to 8. Due to
> > the large segment sizes we use it is extremely unlikely that the
> > secondary hash would ever have been used in practice, so this should not
> > have any negative impacts and may even improve performance.
> 
> Any reason that's not a separate patch?

ok, I'll split it.

> > copro_calculate_slb will now mask the ESID by the correct mask for 1T vs
> 
> Didn't, but will after this patch?

ok, will reword

> > 256M segments. This has no effect by itself as the extra bits were
> > ignored, but it makes debugging the segment table entries easier and
> > means that we can directly compare the ESID values for duplicates
> > without needing to worry about masking in the comparison.
> 
> Separate patch?

ok, I'll split it.

Cheers,
-Ian

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