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

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Date:   Wed, 1 Nov 2023 20:33:48 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     "babu.moger@....com" <babu.moger@....com>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        "Chatre, Reinette" <reinette.chatre@...el.com>,
        "Peter Newman" <peternewman@...gle.com>,
        "x86@...nel.org" <x86@...nel.org>
CC:     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] x86/resctrl: Fix unused variable warning in
 cache_alloc_hsw_probe()

> >     if (wrmsr_safe(MSR_IA32_L3_CBM_BASE, max_cbm, 0))
> >             return;
> >
> > -   rdmsr(MSR_IA32_L3_CBM_BASE, l, h);
> > +   rdmsrl(MSR_IA32_L3_CBM_BASE, l3_cbm_0);
>
> You are writing 32 bit and reading 64 bit. Why don't you change both to 64
> bit?

wrmsr_safe() writes all 64-bits ... just gets those bits as a pair
of 32-bit arguments for the low and high halves.

I could switch that to wrmsrl_safe() and change max_cbm to be "u64"
to make write & read match. Would that be better?

-Tony