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From:   "tan.shaopeng@fujitsu.com" <tan.shaopeng@fujitsu.com>
To:     'James Morse' <james.morse@arm.com>,
        "x86@kernel.org" <x86@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
CC:     Fenghua Yu <fenghua.yu@intel.com>,
        Reinette Chatre <reinette.chatre@intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        H Peter Anvin <hpa@zytor.com>,
        Babu Moger <Babu.Moger@amd.com>,
        "shameerali.kolothum.thodi@huawei.com" 
        <shameerali.kolothum.thodi@huawei.com>,
        Jamie Iles <jamie@nuviainc.com>,
        D Scott Phillips OS <scott@os.amperecomputing.com>,
        "lcherian@marvell.com" <lcherian@marvell.com>,
        "bobo.shaobowang@huawei.com" <bobo.shaobowang@huawei.com>
Subject: RE: [PATCH v2 12/23] x86/resctrl: Abstract and use
 supports_mba_mbps()
Thread-Topic: [PATCH v2 12/23] x86/resctrl: Abstract and use
 supports_mba_mbps()
Thread-Index: AQHXtt30LgJRp3eDk0K08FjK5T6b16vHEhBg
Date:   Thu, 7 Oct 2021 06:13:28 +0000
Message-ID: <TYAPR01MB633002CD0CC9019A98EB517D8BB19@TYAPR01MB6330.jpnprd01.prod.outlook.com>
References: <20211001160302.31189-1-james.morse@arm.com>
 <20211001160302.31189-13-james.morse@arm.com>
In-Reply-To: <20211001160302.31189-13-james.morse@arm.com>
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Hi James,

> To determine whether the mba_MBps option to resctrl should be supported,
> resctrl tests the boot cpus' x86_vendor.
>=20
> This isn't portable, and needs abstracting behind a helper so this check =
can be
> part of the filesystem code that moves to /fs/.
>=20
> Re-use the tests set_mba_sc() does to determine if the mba_sc is supporte=
d
> on this system. An 'alloc_capable' test is added so that support for the =
controls
> isn't implied by the 'delay_linear' property, which is always true for MP=
AM.
>=20
> Signed-off-by: James Morse <james.morse@arm.com>

Reviewed-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>

> ---
> Changes since v1:
>  * Capitalisation
>  * Added MPAM example in commit message
>  * Fixed supports_mba_mbps() logic error in rdt_parse_param()
> ---
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 19 ++++++++++++++-----
>  1 file changed, 14 insertions(+), 5 deletions(-)
>=20
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 069c209be1d5..1207271cce23 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -1948,17 +1948,26 @@ static void mba_sc_destroy(struct rdt_resource
> *r)  }
>=20
>  /*
> - * Enable or disable the MBA software controller
> - * which helps user specify bandwidth in MBps.
>   * MBA software controller is supported only if
>   * MBM is supported and MBA is in linear scale.
>   */
> +static bool supports_mba_mbps(void)
> +{
> +	struct rdt_resource *r =3D
> +&rdt_resources_all[RDT_RESOURCE_MBA].r_resctrl;
> +
> +	return (is_mbm_enabled() &&
> +		r->alloc_capable && is_mba_linear()); }
> +
> +/*
> + * Enable or disable the MBA software controller
> + * which helps user specify bandwidth in MBps.
> + */
>  static int set_mba_sc(bool mba_sc)
>  {
>  	struct rdt_resource *r =3D
> &rdt_resources_all[RDT_RESOURCE_MBA].r_resctrl;
>=20
> -	if (!is_mbm_enabled() || !is_mba_linear() ||
> -	    mba_sc =3D=3D is_mba_sc(r))
> +	if (!supports_mba_mbps() || mba_sc =3D=3D is_mba_sc(r))
>  		return -EINVAL;
>=20
>  	r->membw.mba_sc =3D mba_sc;
> @@ -2317,7 +2326,7 @@ static int rdt_parse_param(struct fs_context *fc,
> struct fs_parameter *param)
>  		ctx->enable_cdpl2 =3D true;
>  		return 0;
>  	case Opt_mba_mbps:
> -		if (boot_cpu_data.x86_vendor !=3D X86_VENDOR_INTEL)
> +		if (!supports_mba_mbps())
>  			return -EINVAL;
>  		ctx->enable_mba_mbps =3D true;
>  		return 0;
> --
> 2.30.2

Regards,
Shaopeng Tan