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From: James Morse <james.morse@arm.com>
To: Robert Richter <rrichter@marvell.com>
Cc: Borislav Petkov <bp@alien8.de>, Tony Luck <tony.luck@intel.com>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	"linux-edac@vger.kernel.org" <linux-edac@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 12/21] EDAC, ghes: Add support for legacy API counters
Date: Wed, 26 Jun 2019 10:33:28 +0100
Message-ID: <043a14f2-3d08-bc81-3a7e-b275179ec1c0@arm.com> (raw)
In-Reply-To: <20190620065527.qqulgpk6k5wva4mj@rric.localdomain>

Hi Robert,

On 20/06/2019 07:55, Robert Richter wrote:
> On 19.06.19 18:22:32, James Morse wrote:
>>> In any case, this patch cleans up code as old API's counter code is
>>> isolated and moved to common code. Making the counter's work for ghes
>>> is actually a side-effect here. The cleanup is a prerequisit for
>>> follow on patches.
>>
>> I'm all for removing/warning-its-broken it when ghes_edac is in use. But the convincing
>> argument is debian ships a 'current' version of edac-utils that predates 199747106934,
>> (that made all this fake csrow stuff deprecated), and debian's popcon says ~1000 people
>> have it installed.
> 
> All arm64 distribution kernels that I have checked come with:
> 
> CONFIG_EDAC_SUPPORT=y
> CONFIG_EDAC=y
> CONFIG_EDAC_LEGACY_SYSFS=y
> # CONFIG_EDAC_DEBUG is not set
> CONFIG_EDAC_GHES=y
> CONFIG_EDAC_LAYERSCAPE=m
> CONFIG_EDAC_THUNDERX=m
> CONFIG_EDAC_XGENE=m

(distros also enable drivers for hardware no-one has!)

Who uses this? edac-utils, on both arm64 and x86.


>> If you want it fixed, please don't do it as a side effect of cleanup. Fixes need to be a
>> small separate series that can be backported. (unless we're confident no-one uses it, in
>> which case, why fix it?)

> It is not that I am keen on fixing legacy edac sysfs. It just happens
> while unifying the error handlers in ghes_edac and edac_mc. As I see
> you are reluctant on just letting it go, let's just disable
> EDAC_LEGACY_SYSFS for ARM64.

That would break other drivers where those legacy counters expose valid values.

You're painting me as some kind of stubborn villan here. You're right my initial reaction
was 'what for?'. Adding new support for legacy counters that have never worked with
ghes_edac looks like the wrong thing to do.

But unfortunately edac-utils is still using this legacy interface.

If we're going to fix it, could we fix it properly? (separate series that can be
backported to stable).


> Though, I don't agree with it as there
> still could be some userland tools that use this interface that cannot
> be used any longer after a transition from x86 to arm64.

I don't think this is the right thing to do. ghes_edac's behaviour should not change
between architectures.


Where we aren't agreeing is how we fix bugs:

Its either broken, and no-one cares, we should remove it.
Or, we should fix it and those fixes should go to stable.

We can't mix fixes and features in a patch series, as the fixes then can't easily be
backported. If its ever in doubt, the patches should still be as separate fixes so the
maintainer can decide.


Thanks,

James

  reply index

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-29  8:44 [PATCH 00/21] EDAC, mc, ghes: Fixes and updates to improve memory error reporting Robert Richter
2019-05-29  8:44 ` [PATCH 01/21] EDAC, mc: Fix edac_mc_find() in case no device is found Robert Richter
2019-05-29  8:44 ` [PATCH 02/21] EDAC: Fixes to use put_device() after device_add() errors Robert Richter
2019-06-11 17:28   ` Borislav Petkov
2019-06-12 17:17     ` Robert Richter
2019-05-29  8:44 ` [PATCH 03/21] EDAC: Kill EDAC_DIMM_PTR() macro Robert Richter
2019-05-29  8:44 ` [PATCH 04/21] EDAC: Kill EDAC_DIMM_OFF() macro Robert Richter
2019-05-29  8:44 ` [PATCH 05/21] EDAC: Introduce mci_for_each_dimm() iterator Robert Richter
2019-05-29  8:44 ` [PATCH 06/21] EDAC, mc: Cleanup _edac_mc_free() code Robert Richter
2019-05-29  8:44 ` [PATCH 07/21] EDAC, mc: Remove per layer counters Robert Richter
2019-05-29  8:44 ` [PATCH 08/21] EDAC, mc: Rework edac_raw_mc_handle_error() to use struct dimm_info Robert Richter
2019-05-29  8:44 ` [PATCH 09/21] EDAC, ghes: Use standard kernel macros for page calculations Robert Richter
2019-05-29 15:13   ` James Morse
2019-05-29  8:44 ` [PATCH 10/21] EDAC, ghes: Remove pvt->detail_location string Robert Richter
2019-05-29 15:13   ` James Morse
2019-06-12 18:13     ` Robert Richter
2019-05-29  8:44 ` [PATCH 11/21] EDAC, ghes: Unify trace_mc_event() code with edac_mc driver Robert Richter
2019-05-29 15:12   ` James Morse
2019-06-03 13:10     ` Robert Richter
2019-06-04 17:15       ` James Morse
2019-06-13 22:23         ` Robert Richter
2019-05-29  8:44 ` [PATCH 12/21] EDAC, ghes: Add support for legacy API counters Robert Richter
2019-05-29 15:13   ` James Morse
2019-06-12 18:41     ` Robert Richter
2019-06-19 17:22       ` James Morse
2019-06-20  6:55         ` Robert Richter
2019-06-26  9:33           ` James Morse [this message]
2019-06-26 10:27             ` Robert Richter
2019-05-29  8:44 ` [PATCH 13/21] EDAC, ghes: Rework memory hierarchy detection Robert Richter
2019-05-29 15:06   ` James Morse
2019-05-31 13:41     ` Robert Richter
2019-05-29  8:44 ` [PATCH 14/21] EDAC, ghes: Extract numa node information for each dimm Robert Richter
2019-05-29 17:51   ` James Morse
2019-06-13 20:52     ` Robert Richter
2019-05-29  8:44 ` [PATCH 15/21] EDAC, ghes: Moving code around ghes_edac_register() Robert Richter
2019-05-29  8:44 ` [PATCH 16/21] EDAC, ghes: Create one memory controller device per node Robert Richter
2019-05-29  8:44 ` [PATCH 17/21] EDAC, ghes: Fill sysfs with the DMI DIMM label information Robert Richter
2019-05-29  8:44 ` [PATCH 18/21] EDAC, mc: Introduce edac_mc_alloc_by_dimm() for per dimm allocation Robert Richter
2019-05-29  8:44 ` [PATCH 19/21] EDAC, ghes: Identify dimm by node, card, module and handle Robert Richter
2019-05-29  8:44 ` [PATCH 20/21] EDAC, ghes: Enable per-layer reporting based on card/module Robert Richter
2019-05-29  8:44 ` [PATCH 21/21] EDAC, Documentation: Describe CPER module definition and DIMM ranks Robert Richter
2019-05-29 14:54 ` [PATCH 00/21] EDAC, mc, ghes: Fixes and updates to improve memory error reporting Borislav Petkov
2019-05-31 14:48   ` Robert Richter

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