linux-kernel - Re: [PATCH v2] x86/resctrl: Fix unused variable warning in cache_alloc_hsw

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Date:   Fri, 3 Nov 2023 13:23:57 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     "Luck, Tony" <tony.luck@...el.com>,
        "Moger, Babu" <babu.moger@....com>
CC:     "Yu, Fenghua" <fenghua.yu@...el.com>,
        Peter Newman <peternewman@...gle.com>,
        "x86@...nel.org" <x86@...nel.org>,
        Shaopeng Tan <tan.shaopeng@...itsu.com>,
        James Morse <james.morse@....com>,
        Jamie Iles <quic_jiles@...cinc.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "patches@...ts.linux.dev" <patches@...ts.linux.dev>
Subject: Re: [PATCH v2] x86/resctrl: Fix unused variable warning in
 cache_alloc_hsw_probe()



On 11/2/2023 3:50 PM, Luck, Tony wrote:
>> This does seem a valid issue and my Ack remains. I'm just puzzled why I do not
>> encounter the same warning.
> 
> Reinette,
> 
> Some other CONFIG option changing CFLAGS?
> 
> Here's what I have for a "make V=1 W=1" for core.o
> 

Tony and I went a bit more back-and-forth on this one and it appears that the
relevant code is optimized out in my build while the same did not happen
for him. 

I can now trigger the warning by enabling Xen support, with CONFIG_PARAVIRT_XXL
causing rdmsr() to be replaced by paravirt_read_msr(). With the relevant code
no longer optimized out, the warning is triggered.

Thanks Tony!

Reinette