Re: [PATCH] MIPS: Add CPU option reporting to /proc/cpuinfo - Kevin 'ldir' Darbyshire-Bryant

From: Kevin 'ldir' Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>
To: Hauke Mehrtens <hauke@hauke-m.de>
Cc: "paul.burton@mips.com" <paul.burton@mips.com>,
	"linux-mips@vger.kernel.org" <linux-mips@vger.kernel.org>,
	"jonas.gorski@gmail.com" <jonas.gorski@gmail.com>
Subject: Re: [PATCH] MIPS: Add CPU option reporting to /proc/cpuinfo
Date: Thu, 3 Jan 2019 23:13:16 +0000	[thread overview]
Message-ID: <DE033D2C-DA1C-49AA-9980-BFB88ED5FB80@darbyshire-bryant.me.uk> (raw)
In-Reply-To: <57008009-6432-7c83-b15b-aa9a9ae567c3@hauke-m.de>


> On 3 Jan 2019, at 21:49, Hauke Mehrtens <hauke@hauke-m.de> wrote:
> 
> On 12/27/18 2:08 PM, Kevin 'ldir' Darbyshire-Bryant wrote:
>>> On 27 Dec 2018, at 12:39, Hauke Mehrtens <hauke@hauke-m.de> wrote:
>>> 
>>>> 
>>> Hi Kevin,
>>> 
>>> I do not see any condition based on CONFIG_MIPS_PERF_SHARED_TC_COUNTERS in arch/mips/include/asm/cpu-features.h, which kernel version did you use to test this patch? cpu_has_mipsmt_pertccounters was introduced between kernel 4.14 and 4.19, so it is not available in older kernel versions.
>>> 
>>> Hauke
>> This is 4.14.90 on openwrt…and I don’t think there are any sneaky backports involved in this area.
>> Take a look around line 131 of arch/mips/kernel/perf_event_mipsxx.c
> 
> Hi Kevin,
> 
> I assume you are talking about this:
> https://elixir.bootlin.com/linux/v4.19.13/source/arch/mips/kernel/perf_event_mipsxx.c#L131

If you look at 4.14.91 https://elixir.bootlin.com/linux/v4.14.91/source/arch/mips/kernel/perf_event_mipsxx.c#L131


> 
> I still do not get why this is a problem.

Hopefully you’ll see why it’s a problem, ‘cos 

#ifdef CONFIG_MIPS_PERF_SHARED_TC_COUNTERS
static int cpu_has_mipsmt_pertccounters;


So I suspect this is my fault/confusion for trying to backport a feature from 4.19 to 4.14 and trying to flag that case - I’m afraid am very time constrained at the moment and I think the best thing is to ignore me :-)

Cheers,

Kevin