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Thread-Topic: [RFC] Kernel Support of Memory Error Detection. 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dkim=pass header.d=amd.com header.s=selector1 header.b=t262R49n; dmarc=pass (policy=quarantine) header.from=amd.com; spf=pass (imf12.hostedemail.com: domain of Vilas.Sridharan@amd.com designates 40.107.94.41 as permitted sender) smtp.mailfrom=Vilas.Sridharan@amd.com; arc=pass ("microsoft.com:s=arcselector9901:i=1") X-Stat-Signature: gtpsdui9oaa17b9to7y8iaa1y8xmgmyq X-HE-Tag: 1668782341-409188 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: [AMD Official Use Only - General] Please include Yazen from AMD on this discussion. Making the patrol scrubber accessible to the OS would very likely not work = without other changes. It is possible (even likely) that other entities in = the system are manipulating the patrol scrubber, and there's no way to reso= lve any conflicts or race conditions. So, if this was exposed to ACPI, it would need to be exposed through a capa= bility and that capability would only be supported if the processors added = support for OS-dedicated patrol scrubber hardware, or if a specific product= could guarantee no other entities are using the patrol scrubber. -Vilas -----Original Message----- From: Jiaqi Yan =20 Sent: Thursday, November 17, 2022 8:20 PM To: Sridharan, Vilas ; Malvestuto, Mike Cc: HORIGUCHI NAOYA(=1B$BKY8}=1B(B =1B$BD>Li=1B(B) ; Nadav Amit ; David Hildenbrand ;= Aktas, Erdem ; pgonda@google.com; rientjes@google.c= om; Hsiao, Duen-wen ; gthelen@google.com; linux-mm@kvac= k.org; jthoughton@google.com; dave.hansen@linux.intel.com; Luck, Tony Subject: Re: [RFC] Kernel Support of Memory Error Detection. Caution: This message originated from an External Source. Use proper cautio= n when opening attachments, clicking links, or responding. On Tue, Nov 8, 2022 at 9:04 PM HORIGUCHI NAOYA(=1B$BKY8}!!D>Li=1B(B) wrote: > > On Tue, Nov 08, 2022 at 04:17:06PM +0000, Luck, Tony wrote: > > > If it is feasible in future that hardware vendors can make patrol=20 > > > scrubber programmable, we can even direct the scanning to patrol=20 > > > scrubber. > > > > There was an attempt to create an ACPI interface for this. I don't=20 > > know if it made it into the standard. > > I briefly checked the latest ACPI spec, and it seems that some=20 > interfaces to control (h/w based) patrol scrubbing are defined. > > https://nam11.safelinks.protection.outlook.com/?url=3Dhttps%3A%2F%2Fuefi > .org%2Fspecs%2FACPI%2F6.5%2F05_ACPI_Software_Programming_Model.html%23 > acpi-ras-feature-table-rasf&data=3D05%7C01%7Cvilas.sridharan%40amd.c > om%7C757b6941a0a7432c826408dac903006a%7C3dd8961fe4884e608e11a82d994e18 > 3d%7C0%7C0%7C638043311988593656%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLj > AwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&a > mp;sdata=3D7%2B4WJc9wS%2B21TAgLw3E1P8qNwSs8V9LFkbDAGU8kgyE%3D&reserv > ed=3D0 A followup question to Intel and AMD RAS folks (Mike and Vilas), what is yo= ur position on the ACPI interface to control hw patrol scrubber, and furthe= r make it programmable by kernel? Is this something you are willing to cons= ider? > > > I didn't do anything with it for Linux because the interface was=20 > > quite complex. > > > > From a h/w perspective it might always be complex. Consecutive=20 > > system physical addresses are generally interleaved across multiple=20 > > memory controllers, channels, DIMMs and ranks. While patrol=20 > > scrubbing may be done by each memory controller at the channel level. > > > > So a simple request to scan a few megabytes of system physical=20 > > address would require address translation to figure out the channel=20 > > addresses on each of the memory controllers and programming each to=20 > > scan the pieces they contribute to the target range. > > I expect that the physical address visible to the kernel is=20 > transparently translated to the real address in which DIMM in which chann= el. > > - Naoya Horiguchi