Received-SPF: softfail (google.com: domain of transitioning linux-kernel-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
Message-ID: <e07c8739-5c8a-8fe9-039c-3a08ce873026@intel.com>
Date:   Tue, 7 Jun 2022 08:51:35 -0700
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101
 Firefox/91.0 Thunderbird/91.10.0
Subject: Re: [PATCH v4 15/21] x86/resctrl: Abstract __rmid_read()
Content-Language: en-US
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>,
        <lcherian@marvell.com>, <bobo.shaobowang@huawei.com>,
        <tan.shaopeng@fujitsu.com>, Jamie Iles <quic_jiles@quicinc.com>,
        Cristian Marussi <cristian.marussi@arm.com>,
        "Xin Hao" <xhao@linux.alibaba.com>, <xingxin.hx@openanolis.org>,
        <baolin.wang@linux.alibaba.com>
References: <20220412124419.30689-1-james.morse@arm.com>
 <20220412124419.30689-16-james.morse@arm.com>
 <39264d40-265e-b41f-913f-c21325678735@intel.com>
 <63845ed3-f09e-43b2-5ded-394bbbd874c4@arm.com>
From:   Reinette Chatre <reinette.chatre@intel.com>
In-Reply-To: <63845ed3-f09e-43b2-5ded-394bbbd874c4@arm.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 7bit
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?UFhFZEt6Nkt4eG1Ma3FyMzdFUXg5TkxrdlFtVldHbmV4VHhseHFjWm10SFdD?=
 =?utf-8?B?MS9XVXowSy9UYzJwaTdhZnVkdFlheXNQMjY3RWs2d0YzOGZhSUlyUTVEMlpo?=
 =?utf-8?B?Qk5USjRuS1lPZjh2TFdnU29IMVdyR0xZQnY3MDhIRTFxZzFUVkRNN2UzaENE?=
 =?utf-8?B?V2lwVDBaeGRLTEZpUVkxSmVCUk5IRU5hczlZQ0pSSEV5Vyt1TVNuNkN0dmc1?=
 =?utf-8?B?SUtWMmIremlQazkwcHpXRWlteEJrcEdMOFhodGZhcVNQUUJhUzQ1alZOMElE?=
 =?utf-8?B?cUtObHZ0cXNXZHlPNk9JL0Uvc3RBaVNDSGRGZzBNdTlLakl0NVoxWTNEVVJB?=
 =?utf-8?B?MTBOWDdxLzNTd0RzZGx2QjZ2TFpxWE1YNFVDSFcyVU1aUWhyVERxcnZuRExs?=
 =?utf-8?B?ZWU0UHZWT3Y3anJXZDArY1VwdGdSRlJxK0JYZm5OSFkzNUFsLzY3QnlCNXpG?=
 =?utf-8?B?ZStheG85TUNTV2RkdS9ETGVnVk9ydUFxeHZUcnFyZk5zUVdBRHdrQlMva21D?=
 =?utf-8?B?OE51RUFzNnlJZ3pzdXo3bkhyN0JtYjEvRzhDUzhJd1JYVWRtVmtGUENYWnVP?=
 =?utf-8?B?dmEzRjNvQThWeVdCTzlGeWV1UWpJbEs2WTNNQVFjSFYyR2NETmJGUkhWN1lm?=
 =?utf-8?B?aktnT0xZQnJxWngxNnQvd2JVblJtVkN5MlMyYjgyR01DaFU4VWlaVW9mNFY4?=
 =?utf-8?B?cXo2SXlGWk5zbDZaNVNkVDE5aWhHY3NSelBDUXRMeW93WE1OenlXbUg2WXMv?=
 =?utf-8?B?QVEzZGdtWlArRlFNZHVQNExWTWw3SGJUWmYyMCtBNk91MkdnbjRsYkdEMkM5?=
 =?utf-8?B?a2wrekJEb2JVZzViUXkvTkZQTG9FaEVSNFlYNTNYZDBISFJpQjl5MGtobWJH?=
 =?utf-8?B?WDVWMlpTT3JrSS9KTTJsZ1VaTWdJQjl3OVliOEl0blJScm5Tc0JCSmV4dFAv?=
 =?utf-8?B?N1EvYU1JNndxMXkvLzZhWVpMZmltUVhCUGdBcTdPRVVSRzQ4cmIzMlhaaFdv?=
 =?utf-8?B?ajI0ZmpqVHhLcG5NTWgrQmNEYmZEYzVZTEdzUTFINjMybnA1U2lBcUluUktS?=
 =?utf-8?B?Q00wck9SaFZTaWhGSVp4eUp1dHZya2RkWlIxdjcwOWtLU0lBcG0rQVR2VVVN?=
 =?utf-8?B?VS9VV3NqdExGZ3N5T3VWM1E5b3hPSnQ1bnR5RGdTVkU3ZGYvUnh4K2hKcys1?=
 =?utf-8?B?L1RlR3Q2cDd0cDQvZXJ4dHg2emhmdXJ3VVhwNHAwdUtVMi95R0s4anV2ZDhI?=
 =?utf-8?B?QUtLYVE3Q0tja05zTDU1QU1wWDRJVnpDaklSWGFVNHp0TjlKd2FWclBkcG5Z?=
 =?utf-8?B?YU5hdnRYT1ZVdzJpeGk3N3dYVTRXbEp6eXlrRHB5NmFVODUvdFB5d1pMSEpx?=
 =?utf-8?B?dkFJQi9QaVJpNklWR2NCODFTL29rWFBHOXI2YktnYWtLM0xScVRoNUhYYzl3?=
 =?utf-8?B?eDBSaXBQZllPcStmdEd3V3h2bnRzeTUrNGcxbFI0bC82K1d0S2lSeUp1YUlR?=
 =?utf-8?B?Mi96Y0JFeE9qSG1zZ0JvMGxaZWhFYXpKT0g3cXNFcWdhS2hoZWFjREdScG5n?=
 =?utf-8?B?bUZWWVFxTi9hdDZaVyszeXA4bitxQUVnbHRiaFB5WGFxSE54b1Y3SC8rM2xr?=
 =?utf-8?B?R3NEdzZuLzRuZU4rbWVkcTc3Zk1uUjhudHMzQmowMU9RK05haG9DbnlyMnZY?=
 =?utf-8?B?Mnl3OGV3VE5YK2xHNG1ZcEY5MUhTR3JFakJsb29SZkYreVVFaXp5TnAySFVZ?=
 =?utf-8?B?cnBBTno0NUFST0Z3SkJ2VkNYQ04wZWErTlQydG1aK0xhSXdxZHFSdlZYV0FS?=
 =?utf-8?B?UUx6aDI5SU5ScUVGNmhJUXFYS0FCVXVjZXVVclduc1UwdWVsMlhlNjVoWnFD?=
 =?utf-8?B?VEV1eXIzUGw5VlJnTVRBUzAvcE43eHoxRzFnbml6UXZmTTZ3WmtiRjRVQVVj?=
 =?utf-8?B?N245UlVydktWS1h5WCtQOVExc3ZOLzZzOC9uOEpKejIxVy9zU0pYQVlXVTlr?=
 =?utf-8?B?NVl6cis3a1NIUkpMQmQ5Z2I0YVk5QWhJNlV6NmI5VnZ3L2ZocUN2dnI0eTQr?=
 =?utf-8?B?Q1AxdCtBZUZqU3lhVGlIcm9PTHZMNzA5OEwxbW9YV0ZJTjlrMndOdDFtZStB?=
 =?utf-8?B?enNtc3JQRmNWR1dvUU16d2kzTGdXdDN3YUhJdnp2eVpuZXZESytjVDNVOWF6?=
 =?utf-8?B?ZWo3eDVCaWhqTndTd0x1RTN6cmFsZ09xTUJ2U2NLOTZaSVgrWkYyVmRRZVZ2?=
 =?utf-8?B?dUExUnRHUjdwY0dvTXBockY1MndHNGlHdkpKc1FXQTFCZEVDK3ViL0hsQUNX?=
 =?utf-8?B?bndGT2RLcEp1M1l5TUpBNEZHcEEvdkkwbmx2OFNINURRa01nSWphTTQ0a1o5?=
 =?utf-8?Q?DpC03bNJV8WN2RVY=3D?=
X-MS-Exchange-CrossTenant-Network-Message-Id: 078380fd-75f9-4e36-a49c-08da489d9ddf
X-MS-Exchange-CrossTenant-AuthSource: BN0PR11MB5744.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 07 Jun 2022 15:51:42.5684
 (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: LzNw6OAfs3W8sYUm+x/oBwdnevRpU7g5bVE3t9kEAEnDgdT+6ab1yGzap4QJKC5Q2viAu/fG//1pPq2Oeo8j+E8uPPJjKudTkwIVo586Vgo=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ0PR11MB5118
X-OriginatorOrg: intel.com
X-Spam-Status: No, score=-4.3 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,
	DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,
	MAILING_LIST_MULTI,NICE_REPLY_A,RDNS_NONE,SPF_HELO_NONE,
	T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no
	version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
	lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Hi James,

On 6/7/2022 5:07 AM, James Morse wrote:
> On 17/05/2022 22:23, Reinette Chatre wrote:
>> On 4/12/2022 5:44 AM, James Morse wrote:
>>
>>> @@ -180,14 +180,24 @@ static u64 __rmid_read(u32 rmid, enum resctrl_event_id eventid)
>>>  	 * are error bits.
>>>  	 */
>>>  	wrmsr(MSR_IA32_QM_EVTSEL, eventid, rmid);
>>> -	rdmsrl(MSR_IA32_QM_CTR, val);
>>> +	rdmsrl(MSR_IA32_QM_CTR, msr_val);
>>>  
>>> -	return val;
>>> +	if (msr_val & RMID_VAL_ERROR)
>>> +		return -EIO;
>>> +	if (msr_val & RMID_VAL_UNAVAIL)
>>> +		return -EINVAL;
>>> +
>>> +	*val = msr_val;
>>> +
>>> +	return 0;
>>>  }
>>>  
>>
>> In above EIO is used to represent RMID_VAL_ERROR ...
>>
>>> @@ -343,7 +355,7 @@ static u64 __mon_event_count(u32 rmid, struct rmid_read *rr)
>>>  		 * Code would never reach here because an invalid
>>>  		 * event id would fail the __rmid_read.
> 
> (I'll fix this comment)
> 
>>>  		 */
>>> -		return RMID_VAL_ERROR;
>>> +		return -EINVAL;
>>>  	}
>>>  
>>>  	if (rr->first) {
>>
>> I understand it can be seen as a symbolic change but could
>> RMID_VAL_ERROR consistently be associated with the same error?
> 
> This one isn't really RMID_VAL_ERROR - it was never read from the hardware, this was an
> invalid argument supplied by the caller.
> 
> You can only hit this if resctrl_arch_rmid_read() doesn't read RMID_VAL_ERROR from the
> hardware, because the hardware supports the event, but its an invalid argument as far as
> this code is concerned.
> 
> I'd prefer to avoid EIO as the error was not reported from hardware - its only reachable
> if the hardware does support the event!

ok, yes, that is fair. I believe no functional change is intended with this change so
please do highlight any such change(s).

Reinette