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Date: Thu, 23 Sep 2021 13:48:52 -0700 From: Jane Chu <jane.chu@...cle.com> To: Dan Williams <dan.j.williams@...el.com>, "Darrick J. Wong" <djwong@...nel.org> Cc: Vishal L Verma <vishal.l.verma@...el.com>, Dave Jiang <dave.jiang@...el.com>, "Weiny, Ira" <ira.weiny@...el.com>, Al Viro <viro@...iv.linux.org.uk>, Matthew Wilcox <willy@...radead.org>, Jan Kara <jack@...e.cz>, Linux NVDIMM <nvdimm@...ts.linux.dev>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, linux-fsdevel <linux-fsdevel@...r.kernel.org> Subject: Re: [PATCH 0/3] dax: clear poison on the fly along pwrite On 9/15/2021 1:27 PM, Dan Williams wrote: >>> I'm also thinking about the MOVEDIR64B instruction and how it >>> might be used to clear poison on the fly with a single 'store'. >>> Of course, that means we need to figure out how to narrow down the >>> error blast radius first. > It turns out the MOVDIR64B error clearing idea runs into problem with > the device poison tracking. Without the explicit notification that > software wanted the error cleared the device may ghost report errors > that are not there anymore. I think we should continue explicit error > clearing and notification of the device that the error has been > cleared (by asking the device to clear it). > Sorry for the late response, I was out for several days. Your concern is understood. I wasn't thinking of an out-of-band MOVDIR64B to clear poison, I was thinking about adding a case to pmem_clear_poison(), such that if CPUID feature shows that MOVDIR64B is supported, instead of calling the BIOS interface to clear poison, MOVDIR64B could be called. The advantage is a. a lot faster; b. smaller radius. And the driver has a chance to update its ->bb record. thanks, -jane
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