linux-kernel - Re: [PATCH 12/33] arm_mpam: Add the class and component structures for ris firmware described

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Message-ID: <5f2c1bf5-6486-464b-aade-4f55b4c3af9f@nvidia.com>
Date: Wed, 27 Aug 2025 18:29:22 -0700
From: Fenghua Yu <fenghuay@...dia.com>
To: James Morse <james.morse@....com>, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-acpi@...r.kernel.org,
 devicetree@...r.kernel.org
Cc: shameerali.kolothum.thodi@...wei.com,
 D Scott Phillips OS <scott@...amperecomputing.com>,
 carl@...amperecomputing.com, lcherian@...vell.com,
 bobo.shaobowang@...wei.com, tan.shaopeng@...itsu.com,
 baolin.wang@...ux.alibaba.com, Jamie Iles <quic_jiles@...cinc.com>,
 Xin Hao <xhao@...ux.alibaba.com>, peternewman@...gle.com,
 dfustini@...libre.com, amitsinght@...vell.com,
 David Hildenbrand <david@...hat.com>, Rex Nie <rex.nie@...uarmicro.com>,
 Dave Martin <dave.martin@....com>, Koba Ko <kobak@...dia.com>,
 Shanker Donthineni <sdonthineni@...dia.com>, baisheng.gao@...soc.com,
 Jonathan Cameron <jonathan.cameron@...wei.com>, Rob Herring
 <robh@...nel.org>, Rohit Mathew <rohit.mathew@....com>,
 Rafael Wysocki <rafael@...nel.org>, Len Brown <lenb@...nel.org>,
 Lorenzo Pieralisi <lpieralisi@...nel.org>, Hanjun Guo
 <guohanjun@...wei.com>, Sudeep Holla <sudeep.holla@....com>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Catalin Marinas <catalin.marinas@....com>,
 Will Deacon <will@...nel.org>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Danilo Krummrich <dakr@...nel.org>, Ben Horgan <ben.horgan@....com>
Subject: Re: [PATCH 12/33] arm_mpam: Add the class and component structures
 for ris firmware described

Hi, James,

On 8/22/25 08:29, James Morse wrote:
> An MSC is a container of resources, each identified by their RIS index.
> Some RIS are described by firmware to provide their position in the system.
> Others are discovered when the driver probes the hardware.
>
> To configure a resource it needs to be found by its class, e.g. 'L2'.
> There are two kinds of grouping, a class is a set of components, which
> are visible to user-space as there are likely to be multiple instances
> of the L2 cache. (e.g. one per cluster or package)
>
> struct mpam_components are a set of struct mpam_vmsc. A vMSC groups the
> RIS in an MSC that control the same logical piece of hardware. (e.g. L2).
> This is to allow hardware implementations where two controls are presented
> as different RIS. Re-combining these RIS allows their feature bits to
> be or-ed. This structure is not visible outside mpam_devices.c
>
> struct mpam_vmsc are then a set of struct mpam_msc_ris, which are not
> visible as each L2 cache may be composed of individual slices which need
> to be configured the same as the hardware is not able to distribute the
> configuration.
>
> Add support for creating and destroying these structures.
>
> A gfp is passed as the structures may need creating when a new RIS entry
> is discovered when probing the MSC.
>
> CC: Ben Horgan <ben.horgan@....com>
> Signed-off-by: James Morse <james.morse@....com>
> ---
> Changes since RFC:
>   * removed a pr_err() debug message that crept in.
> ---
>   drivers/resctrl/mpam_devices.c  | 488 +++++++++++++++++++++++++++++++-
>   drivers/resctrl/mpam_internal.h |  91 ++++++
>   include/linux/arm_mpam.h        |   8 +-
>   3 files changed, 574 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
> index 71a1fb1a9c75..5baf2a8786fb 100644
> --- a/drivers/resctrl/mpam_devices.c
> +++ b/drivers/resctrl/mpam_devices.c
[SNIP]
> +static struct mpam_vmsc *
> +mpam_vmsc_alloc(struct mpam_component *comp, struct mpam_msc *msc, gfp_t gfp)
> +{
> +	struct mpam_vmsc *vmsc;
> +
> +	lockdep_assert_held(&mpam_list_lock);
> +
> +	vmsc = kzalloc(sizeof(*vmsc), gfp);
> +	if (!comp)

s/if (!cmp)/if (!vmsc)/


> +		return ERR_PTR(-ENOMEM);
> +	init_garbage(vmsc);
> +
> +	INIT_LIST_HEAD_RCU(&vmsc->ris);
> +	INIT_LIST_HEAD_RCU(&vmsc->comp_list);
> +	vmsc->comp = comp;
> +	vmsc->msc = msc;
> +
> +	list_add_rcu(&vmsc->comp_list, &comp->vmsc);
> +
> +	return vmsc;
> +}

Thanks.

-Fenghua