linux-kernel - RE: [PATCH v2 02/18] x86/resctrl: Access per-rmid structures by index

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Message-ID: <IA1PR11MB6097E206D4A9404BC3D78CD89BC69@IA1PR11MB6097.namprd11.prod.outlook.com>
Date:   Tue, 17 Jan 2023 18:29:08 +0000
From:   "Yu, Fenghua" <fenghua.yu@...el.com>
To:     James Morse <james.morse@....com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "Chatre, Reinette" <reinette.chatre@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        H Peter Anvin <hpa@...or.com>,
        Babu Moger <Babu.Moger@....com>,
        "shameerali.kolothum.thodi@...wei.com" 
        <shameerali.kolothum.thodi@...wei.com>,
        D Scott Phillips OS <scott@...amperecomputing.com>,
        "carl@...amperecomputing.com" <carl@...amperecomputing.com>,
        "lcherian@...vell.com" <lcherian@...vell.com>,
        "bobo.shaobowang@...wei.com" <bobo.shaobowang@...wei.com>,
        "tan.shaopeng@...itsu.com" <tan.shaopeng@...itsu.com>,
        "xingxin.hx@...nanolis.org" <xingxin.hx@...nanolis.org>,
        "baolin.wang@...ux.alibaba.com" <baolin.wang@...ux.alibaba.com>,
        Jamie Iles <quic_jiles@...cinc.com>,
        Xin Hao <xhao@...ux.alibaba.com>,
        "peternewman@...gle.com" <peternewman@...gle.com>
Subject: RE: [PATCH v2 02/18] x86/resctrl: Access per-rmid structures by index

Hi, James,

> Because of the differences between Intel RDT/AMD QoS and Arm's MPAM
> monitors, RMID values on arm64 are not unique unless the CLOSID is also
> included. Bitmaps like rmid_busy_llc need to be sized by the number of unique
> entries for this resource.
> 
> Add helpers to encode/decode the CLOSID and RMID to an index. The domain's
> busy_rmid_llc and the rmid_ptrs[] array are then sized by index. On x86, this is
> always just the RMID. This gives resctrl a unique value it can use to store
> monitor values, and allows MPAM to decode the closid when reading the
> hardware counters.
> 
> Tested-by: Shaopeng Tan <tan.shaopeng@...itsu.com>
> Signed-off-by: James Morse <james.morse@....com>
> ---
> Changes since v1:
>  * Added X86_BAD_CLOSID macro to make it clear what this value means
>  * Added second WARN_ON() for closid checking, and made both _ONCE()
> ---
>  arch/x86/include/asm/resctrl.h         | 24 ++++++++
>  arch/x86/kernel/cpu/resctrl/internal.h |  2 +
> arch/x86/kernel/cpu/resctrl/monitor.c  | 79 +++++++++++++++++---------
> arch/x86/kernel/cpu/resctrl/rdtgroup.c |  7 ++-
>  4 files changed, 82 insertions(+), 30 deletions(-)
> 
> diff --git a/arch/x86/include/asm/resctrl.h b/arch/x86/include/asm/resctrl.h
> index 52788f79786f..44d568f3577c 100644
> --- a/arch/x86/include/asm/resctrl.h
> +++ b/arch/x86/include/asm/resctrl.h
> @@ -7,6 +7,13 @@
>  #include <linux/sched.h>
>  #include <linux/jump_label.h>
> 
> +/*
> + * This value can never be a valid CLOSID, and is used when mapping a
> + * (closid, rmid) pair to an index and back. On x86 only the RMID is
> + * needed.
> + */
> +#define X86_RESCTRL_BAD_CLOSID		~0
> +
>  /**
>   * struct resctrl_pqr_state - State cache for the PQR MSR
>   * @cur_rmid:		The cached Resource Monitoring ID
> @@ -94,6 +101,23 @@ static inline void resctrl_sched_in(void)
>  		__resctrl_sched_in();
>  }
> 
> +static inline u32 resctrl_arch_system_num_rmid_idx(void)
> +{
> +	/* RMID are independent numbers for x86. num_rmid_idx==num_rmid
> */
> +	return boot_cpu_data.x86_cache_max_rmid + 1; }
> +
> +static inline void resctrl_arch_rmid_idx_decode(u32 idx, u32 *closid,
> +u32 *rmid) {
> +	*rmid = idx;
> +	*closid = X86_RESCTRL_BAD_CLOSID;
> +}
> +
> +static inline u32 resctrl_arch_rmid_idx_encode(u32 closid, u32 rmid) {

s/u32 closid/u32 ignored/, please.

> +	return rmid;
> +}
> +

Thanks.

-Fenghua