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X-OriginatorOrg: micron.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 Mar 2024 10:16:01.5783 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 639fb919-40a3-442e-52a0-08dc3cfd4250 X-MS-Exchange-CrossTenant-Id: f38a5ecd-2813-4862-b11b-ac1d563c806f X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f38a5ecd-2813-4862-b11b-ac1d563c806f;Ip=[137.201.242.130];Helo=[mail.micron.com] X-MS-Exchange-CrossTenant-AuthSource: CY4PEPF0000E9D5.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CO1PR08MB6596 > -----Original Message----- > From: Dan Williams > Sent: Tuesday, March 5, 2024 2:10 AM > To: Srinivasulu Opensrc ; linux- > cxl@vger.kernel.org; linux-mm@kvack.org > Cc: Jonathan.Cameron@huawei.com; dan.j.williams@intel.com; > john@jagalactic.com; Eishan Mirakhur ; Ajay Joshi > ; Ravis OpenSrc ; > Srinivasulu Thanneeru > Subject: [EXT] Re: [PATCH v2 0/2] Add log related mailbox commands >=20 > CAUTION: EXTERNAL EMAIL. Do not click links or open attachments unless > you recognize the sender and were expecting this message. >=20 >=20 > Any specific reason to include linux-mm on this enabling? I suspect this > topic is only of interest to linux-cxl. Lets drop linux-mm from a v3 > posting. Sorry, it's a copy paste mistake. Agreed, will drop linux-mm from V3.=20 >=20 > sthanneeru.opensrc@ wrote: > > From: Srinivasulu Thanneeru > > > > Add support to expose following mailbox commands to userspace > > for clearing and populating the Vendor debug log and > > Component State dump log in certain scenarios, > > allowing for the aggregation of results over time. >=20 > What is missing for me here is why the ioctl() ABI is suitable for both > of these. The Vendor Debug Log seems straightforward to enable via > ioctl() since there is no background operation entanglement, no > population complexity, and no reference to other payloads. >=20 > The Component State Dump has several caveats in my mind for ioctl() not > being a suitable ABI: >=20 > 1/ Populate Log has an unreasonable expectation that the submitter can > monopolize the mailbox indefinitely. At least that can be solved by > Linux only supporting automatically populated Component State Dump logs. >=20 > 2/ Automatic log population requires the caller to handle races with > auto-population. The kernel need not export that complexity to > userspace. This is not fatal to the proposal, but it has interactions > with caveat 3. >=20 > 3/ The Component State Dump format wants to reference events in the > Event Log, if the Event Log has been cleared then, per the spec, the > Component State Dump must not reference the Event Handle. To me that > implies that the code that clears event records must be careful to not > destroy linkage to component state information. That suggests that the > proper place to dump the component state log is an addendum to the > current trace events, before that code clears the event record. >=20 > Something roughly like this: Thank you for suggesting this approach. Next version V3, will add "clear log" for Component State Dump separately, as suggested bellow. Probably as a separate patch. >=20 > diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c > index 9adda4795eb7..498b2a0b3e76 100644 > --- a/drivers/cxl/core/mbox.c > +++ b/drivers/cxl/core/mbox.c > @@ -941,7 +941,8 @@ static int cxl_clear_event_record(struct > cxl_memdev_state *mds, > } >=20 > static void cxl_mem_get_records_log(struct cxl_memdev_state *mds, > - enum cxl_event_log_type type) > + enum cxl_event_log_type type, > + struct cxl_component_state_dump *csd) > { > struct cxl_memdev *cxlmd =3D mds->cxlds.cxlmd; > struct device *dev =3D mds->cxlds.dev; > @@ -977,9 +978,12 @@ static void cxl_mem_get_records_log(struct > cxl_memdev_state *mds, > if (!nr_rec) > break; >=20 > - for (i =3D 0; i < nr_rec; i++) > + for (i =3D 0; i < nr_rec; i++) { > __cxl_event_trace_record(cxlmd, type, > &payload->records[i]); > + if (is_event_referenced(csd, type, &payload->reco= rds[i])) > + trace_csd(csd, ...); > + } >=20 > if (payload->flags & CXL_GET_EVENT_FLAG_OVERFLOW) > trace_cxl_overflow(cxlmd, type, payload); >=20 > ...but in general this cover letter needs to comment on the long term > suitability of the ABI. Will add more details to cover letter in V3.