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Date:   Wed, 1 Nov 2023 16:43:12 +0700
From:   Bagas Sanjaya <bagasdotme@gmail.com>
To:     Tony Luck <tony.luck@intel.com>, Fenghua Yu <fenghua.yu@intel.com>,
        Reinette Chatre <reinette.chatre@intel.com>,
        Peter Newman <peternewman@google.com>, x86@kernel.org
Cc:     Shaopeng Tan <tan.shaopeng@fujitsu.com>,
        James Morse <james.morse@arm.com>,
        Jamie Iles <quic_jiles@quicinc.com>,
        Babu Moger <babu.moger@amd.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        linux-kernel@vger.kernel.org, patches@lists.linux.dev
Subject: Re: [PATCH] x86/resctrl: Fix unused variable warning in
 cache_alloc_hsw_probe()
Message-ID: <ZUIdsK5LGmRww9ER@debian.me>
References: <20231031220534.37730-1-tony.luck@intel.com>
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On Tue, Oct 31, 2023 at 03:05:34PM -0700, Tony Luck wrote:
> In a "W=3D1" build gcc throws a warning:
>=20
> arch/x86/kernel/cpu/resctrl/core.c: In function =E2=80=98cache_alloc_hsw_=
probe=E2=80=99:
> arch/x86/kernel/cpu/resctrl/core.c:139:16: warning: variable =E2=80=98h=
=E2=80=99 set but not used
>=20
> Fix by switching from rdmsr() to rdmsrl() using a single u64 argument
> for the MSR value instead of the pair of u32 for the high and low
> halves.
>=20
> Signed-off-by: Tony Luck <tony.luck@intel.com>
> ---
> This has been annoying me for a while as the only warning from the
> resctrl code when building with W=3D1.
>=20
> N.B. compile tested only. I don't have a Haswell system to check this wor=
ks.
>=20
>  arch/x86/kernel/cpu/resctrl/core.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>=20
> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/res=
ctrl/core.c
> index 19e0681f0435..4084131d391d 100644
> --- a/arch/x86/kernel/cpu/resctrl/core.c
> +++ b/arch/x86/kernel/cpu/resctrl/core.c
> @@ -136,15 +136,16 @@ static inline void cache_alloc_hsw_probe(void)
>  {
>  	struct rdt_hw_resource *hw_res =3D &rdt_resources_all[RDT_RESOURCE_L3];
>  	struct rdt_resource *r  =3D &hw_res->r_resctrl;
> -	u32 l, h, max_cbm =3D BIT_MASK(20) - 1;
> +	u32 max_cbm =3D BIT_MASK(20) - 1;
> +	u64 l3_cbm_0;
> =20
>  	if (wrmsr_safe(MSR_IA32_L3_CBM_BASE, max_cbm, 0))
>  		return;
> =20
> -	rdmsr(MSR_IA32_L3_CBM_BASE, l, h);
> +	rdmsrl(MSR_IA32_L3_CBM_BASE, l3_cbm_0);
> =20
>  	/* If all the bits were set in MSR, return success */
> -	if (l !=3D max_cbm)
> +	if (l3_cbm_0 !=3D max_cbm)
>  		return;
> =20
>  	hw_res->num_closid =3D 4;

No noticeable regressions on my Acer Aspire E15 (the laptop uses Intel Core
i3 Haswell), thanks!

Tested-by: Bagas Sanjaya <bagasdotme@gmail.com>

--=20
An old man doll... just what I always wanted! - Clara

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