Received-SPF: pass (google.com: domain of linux-kernel+bounces-136198-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) client-ip=2604:1380:45e3:2400::1;
Message-ID: <d598767d-1c44-4417-9dc6-7078c97df39f@intel.com>
Date: Mon, 8 Apr 2024 20:23:36 -0700
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH v1 18/31] x86/resctrl: Allow
 resctrl_arch_mon_event_config_write() to return an error
To: James Morse <james.morse@arm.com>, <x86@kernel.org>,
	<linux-kernel@vger.kernel.org>
CC: Fenghua Yu <fenghua.yu@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>, D Scott Phillips OS
	<scott@os.amperecomputing.com>, <carl@os.amperecomputing.com>,
	<lcherian@marvell.com>, <bobo.shaobowang@huawei.com>,
	<tan.shaopeng@fujitsu.com>, <baolin.wang@linux.alibaba.com>, Jamie Iles
	<quic_jiles@quicinc.com>, Xin Hao <xhao@linux.alibaba.com>,
	<peternewman@google.com>, <dfustini@baylibre.com>, <amitsinght@marvell.com>,
	David Hildenbrand <david@redhat.com>, Rex Nie <rex.nie@jaguarmicro.com>,
	"Dave Martin" <dave.martin@arm.com>
References: <20240321165106.31602-1-james.morse@arm.com>
 <20240321165106.31602-19-james.morse@arm.com>
Content-Language: en-US
From: Reinette Chatre <reinette.chatre@intel.com>
In-Reply-To: <20240321165106.31602-19-james.morse@arm.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 7bit
Precedence: bulk
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?ZWpndXlhTW1GeE5IZzkxaHRPUFhRREI1SnBTS29pMElBM2xTV3VIYTNZaE0z?=
 =?utf-8?B?dTMxS2RkTDJmL0FYV1VES2VhWnNqUnpCSXU2a1p5dkpIM2kyeEhvcmxLcXZo?=
 =?utf-8?B?RHpOQ3IvMmdldytsUDd2MlBPZ0VCVkI2OURBQVgvTng0NUVlVG13YjRuczZz?=
 =?utf-8?B?TnhLTUJYL0ZxME5Na0MwZzR3VkY2WGxjZ1FDa1NkWDY3dE5nNjg2Nkc0L3Ix?=
 =?utf-8?B?WHd6eGlIV3JVR0FWR1VoUzJnTyt1OUlhQkVYTDUyOC9Pb0dLRXROaTU2WWM5?=
 =?utf-8?B?SytjK09QREJpMWwrZ0ZJR29LazROUHV5bUQxeVRqMG92RzI2Vi9jOFlCYTc0?=
 =?utf-8?B?VEl6a3NmSUpjZ2xRUjRzUVMwNDRrSFlXWDg4RVJnY29JMHZGaGhCekZWZSto?=
 =?utf-8?B?ZUFtZy80eUo4SkltSEN5bDAwT3hFU1g4QnBLM3hMUHRPOWVRb0xXQUVJMERa?=
 =?utf-8?B?QldMNURSTVBOc3A2cFg3ZTVCdTEvWEh6VXgxb1lYWmNYdmtReVg2TTBXUjVz?=
 =?utf-8?B?OHFGN29UakJrK2ZHRTdQdTczWHRaMGFILzZQbHh6WW9hM1RrWmRQNWRUaCtK?=
 =?utf-8?B?aDlvQVZlbXloOUpFRWVuNjEzYjJJalhhcjZjWjhxb0FlQ29RaklOUVo5RCsz?=
 =?utf-8?B?WjhrWnhMUnk0QWVtbmNUQUZrU2VGUWRvVjBuQ2ZpK1Z1N3pkamFDVTRtOEZZ?=
 =?utf-8?B?NE1OeTRxN2RIRHVRUXB2L21wa3RxRThFdzBRWkdGTUQ2U1pFam80aklZNGRl?=
 =?utf-8?B?b0lPVlJSWVc3Z3JTTE1SYkJWc3Z5cTlHWmJ5bXBTVVlMY1ZZRFQ0Q2VWTkFy?=
 =?utf-8?B?TFBQQWRPaXh0MmpkR29KTFhXZ3hxOXJKcUgyQnFPVGxGNlZpQ1pFbkdhcEVB?=
 =?utf-8?B?VHJEYlZ6TUtxVEJWeEZkeHZFU0RFMVZ6UUdjRldRR3RTNE93SnR5R0x3SnVU?=
 =?utf-8?B?SmJqVmd6SnNISHR4VGwrUFR0c0JmL3k4Zmx2VDBWUk1SV21JSDE2czJ4U21R?=
 =?utf-8?B?bC9vWE9HREIwZzdTdEpCc1BaaWhKNGxjM29MS1NOVkZrSGMzWTI1aEFwcXVY?=
 =?utf-8?B?VlBOVUMxZ3JvV2Jnc0ZFYm9VeE84MW5QK280dmVBS0JPZDZkcjY0Y1Mzcy9k?=
 =?utf-8?B?S1hlb3hjTHRvMkpVZys4RXllbzlTVnhhUXZadHdpMFRFcWltLzBiOGxkRFhO?=
 =?utf-8?B?ZGt2MTlHaVgzKzBqVHVhbElwQzA2Y1lKclBkMHN0QkdaMFpNY29mTFVEanlN?=
 =?utf-8?B?NGw4Mk9PUmhtaFNSdDgzSmZjTU84UzZwWDNhMllzZXNYVm5qcG43dnorSnFW?=
 =?utf-8?B?eG5ST2tTM0ZmY0ZoQzFPWTZOT2dPcGlIMWFJN2lZQ0tzSjNpd3NIWU9EQzhN?=
 =?utf-8?B?c0Y2RExaWEpubVJtaTRJcW4rZXl6MHEzL2pQUGkrdklqTGZTMHB2UnR3eUpK?=
 =?utf-8?B?OUtmemFnRFJrM2NDYjFwWlNMVTJHcG8zNERLTnIva20vL2RFZjQyNllQdU5X?=
 =?utf-8?B?eUtMQnJLZm42bElZY2JEQkViNHBFcTIrdmVXSEtlaTU2dVZLcVcxakJVT0Ev?=
 =?utf-8?B?ZkNFUnU2WTVkNFE5ak1GS3VRMDh6dFVpeWtxcVZEM2puVm9jSWNzOU9NUkdm?=
 =?utf-8?B?SDJ4MXZOVk9tQlBBbFBZRWc4OWFDNGI3aUYzTFBwMWhtVmZmNXlBRFFOT3hz?=
 =?utf-8?B?QVVHb3hBbFZYK0MyeGs3S1lkbGFIWWg3WExmUVIzVHZyQThTeDRRcmk0Qmdy?=
 =?utf-8?B?d2JQVzUzY0d1cmdoeHFtZHFGYjd4K2VOUTFnM0tETzdYdGVtM25VZHpoSkFB?=
 =?utf-8?B?RzlwSXFTU0s1SGJoMUtVNXFyb0xNUkZaVHF6eUtTOE1Jb1hjUTR6VkVNakU3?=
 =?utf-8?B?VmpaR3Y3aEVOSlVFMDJnV2RTVmZCb0pnL1NOeTdDYzV4aGE3SURzVVB0QjdZ?=
 =?utf-8?B?bUkzS2t6L0lBQTlGdkVUSzM1TUQrUkt1dlIvUnBmWE9DNDIyUG15SUsvZHpa?=
 =?utf-8?B?M1JsaXN1NlhRNC9SRE1jbTd3VGpWNlcwZWsxb05Cd1JYSGROVEZRUVNNeERU?=
 =?utf-8?B?RjlMeDdMMzc0dHdmYkFrTDM3WmJxZVp5YVROekI3VDFvZ0pybUQ2bitjRWgx?=
 =?utf-8?B?ZWY0RGNWZEh6S2g4c0RSODE1am5kRVJseEludy9EWEJNN3BPRWRVRExPUzdT?=
 =?utf-8?B?SVE9PQ==?=
X-MS-Exchange-CrossTenant-Network-Message-Id: a001ba28-1019-4660-6c0d-08dc58447315
X-MS-Exchange-CrossTenant-AuthSource: SJ2PR11MB7573.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 09 Apr 2024 03:23:39.2703
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: Kv5z/M6HOMp/5kbHDwEde3sxs+HGqgitkvaIgu9iObUlhdrVVZcJGQThJr59aGOamusM1PnwIrFYPz9Ir9DzfEvBNGcLdgZN1e1E4omeb8o=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR11MB6357
X-OriginatorOrg: intel.com

Hi James,

On 3/21/2024 9:50 AM, James Morse wrote:
> resctrl_arch_mon_event_config_write() writes a bitmap of events provided
> by user-space into the configuration register for the monitors.
> 
> This assumes that all architectures support all the features each bit
> corresponds to.
> 
> MPAM can filter monitors based on read, write, or both, but there are
> many more options in the existing bitmap. To allow this interface to
> work for machines with MPAM, allow the architecture helper to return
> an error if an incompatible bitmap is set.
> 
> When valid values are provided, there is no change in behaviour. If
> an invalid value is provided, currently it is silently ignored, but
> last_cmd_status is updated. After this change, the parser will stop
> at the first invalid value and return an error to user-space. This
> matches the way changes to the schemata file are made.
> 

Is this needed? With move of mbm_cfg_mask to rdt_resource I expect
MPAM would use it to set what the valid values are. With that done,
when user space provides a value, mon_config_write() compares user
provided value against mbm_cfg_mask and will already return early
(before attempting to write to hardware) with error
if value is not supported. This seems to accomplish the goal of this
patch?

> Signed-off-by: James Morse <james.morse@arm.com>
> ---

..
> diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
> index 8a7367d1ce45..6705d7960dfd 100644
> --- a/include/linux/resctrl.h
> +++ b/include/linux/resctrl.h
> @@ -200,6 +200,7 @@ struct resctrl_mon_config_info {
>  	struct rdt_domain   *d;
>  	u32                  evtid;
>  	u32                  mon_config;
> +	int                  err;
>  };

Please take care to use consistent spacing.

Reinette