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Mon, 08 Dec 2025 09:43:58 -0800 (PST) Received: from localhost ([2a01:4b00:b703:c200:1ac0:4dff:fe39:5426]) by smtp.gmail.com with UTF8SMTPSA id 5b1f17b1804b1-479308cd87csm269816035e9.0.2025.12.08.09.43.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 08 Dec 2025 09:43:58 -0800 (PST) From: Punit Agrawal To: Reinette Chatre Cc: Punit Agrawal , James Morse , Ben Horgan , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v6 00/34] arm_mpam: Add basic mpam driver In-Reply-To: <5261337c-337d-44ca-aff1-0a927b81e593@intel.com> (Reinette Chatre's message of "Fri, 5 Dec 2025 11:11:34 -0800") References: <20251119122305.302149-1-ben.horgan@arm.com> <877bvfa23i.fsf@stealth> <87sedrlsjk.fsf@stealth> <642767c9-f926-490a-83a1-160978c37553@arm.com> <871pl9krdz.fsf@stealth> <5261337c-337d-44ca-aff1-0a927b81e593@intel.com> Date: Mon, 08 Dec 2025 17:43:57 +0000 Message-ID: <87tsy0kgwy.fsf@stealth> User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-Authority-Analysis: v=2.4 cv=ee0wvrEH c=1 sm=1 tr=0 ts=69370e60 cx=c_pps a=oc9J++0uMp73DTRD5QyR2A==:117 a=xqWC_Br6kY4A:10 a=wP3pNCr1ah4A:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VwQbUJbxAAAA:8 a=7CQSdrXTAAAA:8 a=QyXUC8HyAAAA:8 a=SgM2RwbWsAO8Gts_S_MA:9 a=iYH6xdkBrDN1Jqds4HTS:22 a=a-qgeE7W1pNrGK8U0ZQC:22 X-Proofpoint-GUID: ALYK97EB2wjm7w8b0T8VKJmogYfaBSmh X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMjA4MDE1MCBTYWx0ZWRfXyrwAvrKywXof JQsrphZPSQstm78q2PPgD5842O6SL5OPCf/2seF2b+H2tm7A2Db1njS3N+j6jowjQ6zpp0gEkSI Ih1NU61EwRoN0MYVRbQ93V4RR4xY0EQoRNJlIg7nmE1ZWd54TL+cMAizuzpwEZwraJ2u9T4TNGZ l6pT2tYo/CUTlCwDpO4G4gxCVgsfL/Eqi8Q1BJmyTE2lxslOcK1wkM156clr0EZ5pu4u7oyGnJI 8zJjkL95ZfHgObTyT9NaOA/1/gpISLlAvyLULmObanTlmDWZ/2sBrL/8z63RZKsT1cYHuUca3am 5no42dghSYV3YfT9nCcXs05tUGdkti/AUlTg6yM1E1+v8X2gmAWCWzBInpr72cLMIpzJuBCUUYs cL9ep2X3XpguMLkyeGRnurLhg10peg== X-Proofpoint-ORIG-GUID: ALYK97EB2wjm7w8b0T8VKJmogYfaBSmh X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.100.49 definitions=2025-12-06_02,2025-12-04_04,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 clxscore=1015 priorityscore=1501 spamscore=0 bulkscore=0 phishscore=0 suspectscore=0 impostorscore=0 malwarescore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2510240001 definitions=main-2512080150 Hi Reinette, Reinette Chatre writes: > Hi Punit, > > On 12/5/25 5:08 AM, Punit Agrawal wrote: >> James Morse writes: >>> On 03/12/2025 11:21, Punit Agrawal wrote: >>>> Ben Horgan writes: >>>>> On 11/24/25 15:21, Punit Agrawal wrote: > >>>>>> The platform has MSCs attached >>>>>> to shared L2 caches which are being skipped during later stages of >>>>>> initialisation. IIUC, the L2 MSCs' limitations stems from the >>>>>> assumptions in the resctrl interface. >>>>> >>>>> What in particualar is being skipped? >>> >>>> The registration of the discovered MSCs with resctrl and subsequent >>>> exposing it to the user. >>> >>> resctrl's 'L2' support is limited to the CPOR bitmap. >>> If you have controls, there is no resctrl 'event' that can exposed them. >>> (the problem being they all have 'L3' in the name!) >> >>>>>> I was wondering if there are any patches available to relax these >>>>>> limitations? >> >>> Knowing which property it is will help - but some of these things are checked >>> to match resctrl's ABI. They can't necessarily be relaxed without breaking >>> user-space. >> >> This platform has portion, capacity and priority partitioning, as well >> as memory bandwidth and cache storage monitoring. The MPAM code seems to >> correctly parse the properties. >> >> But as you point out, the resctrl 'L2' support doesn't have anything >> other than CPOR bitmap yet. Have you looked at what's needed to extend >> resctrl to support some of the others? > > Please see [1] for a summary of ideas on how resctrl can support multiple > controls. Nothing is final, please do add your ideas and requirements. > > There are a couple of opens not included in the summary. If interested > [2] is where a lot of discussion happened that prompted the need for > a summary. Thanks a lot for the pointers. Let me catch up with what's already discussed and raise any points that are not clear / need refining. > > Reinette > > [1] https://lore.kernel.org/lkml/aPtfMFfLV1l%2FRB0L@e133380.arm.com/ > [2] https://lore.kernel.org/lkml/aNFliMZTTUiXyZzd@e133380.arm.com/