Messages in this thread | | | From | Jane Chu <> | Subject | Re: [PATCH] acpi/nfit: badrange report spill over to clean range | Date | Wed, 13 Jul 2022 23:52:13 +0000 |
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On 7/12/2022 5:48 PM, Dan Williams wrote: > Jane Chu wrote: >> Commit 7917f9cdb503 ("acpi/nfit: rely on mce->misc to determine poison >> granularity") changed nfit_handle_mce() callback to report badrange for >> each poison at an alignment indicated by 1ULL << MCI_MISC_ADDR_LSB(mce->misc) >> instead of the hardcoded L1_CACHE_BYTES. However recently on a server >> populated with Intel DCPMEM v2 dimms, it appears that >> 1UL << MCI_MISC_ADDR_LSB(mce->misc) turns out is 4KiB, or 8 512-byte blocks. >> Consequently, injecting 2 back-to-back poisons via ndctl, and it reports >> 8 poisons. >> >> [29076.590281] {3}[Hardware Error]: physical_address: 0x00000040a0602400 >> [..] >> [29076.619447] Memory failure: 0x40a0602: recovery action for dax page: Recovered >> [29076.627519] mce: [Hardware Error]: Machine check events logged >> [29076.634033] nfit ACPI0012:00: addr in SPA 1 (0x4080000000, 0x1f80000000) >> [29076.648805] nd_bus ndbus0: XXX nvdimm_bus_add_badrange: (0x40a0602000, 0x1000) >> [..] >> [29078.634817] {4}[Hardware Error]: physical_address: 0x00000040a0602600 >> [..] >> [29079.595327] nfit ACPI0012:00: addr in SPA 1 (0x4080000000, 0x1f80000000) >> [29079.610106] nd_bus ndbus0: XXX nvdimm_bus_add_badrange: (0x40a0602000, 0x1000) >> [..] >> { >> "dev":"namespace0.0", >> "mode":"fsdax", >> "map":"dev", >> "size":33820770304, >> "uuid":"a1b0f07f-747f-40a8-bcd4-de1560a1ef75", >> "sector_size":512, >> "align":2097152, >> "blockdev":"pmem0", >> "badblock_count":8, >> "badblocks":[ >> { >> "offset":8208, >> "length":8, >> "dimms":[ >> "nmem0" >> ] >> } >> ] >> } >> >> So, 1UL << MCI_MISC_ADDR_LSB(mce->misc) is an unreliable indicator for poison >> radius and shouldn't be used. More over, as each injected poison is being >> reported independently, any alignment under 512-byte appear works: >> L1_CACHE_BYTES (though inaccurate), or 256-bytes (as ars->length reports), >> or 512-byte. >> >> To get around this issue, 512-bytes is chosen as the alignment because >> a. it happens to be the badblock granularity, >> b. ndctl inject-error cannot inject more than one poison to a 512-byte block, >> c. architecture agnostic > > I am failing to see the kernel bug? Yes, you injected less than 8 > "badblocks" of poison and the hardware reported 8 blocks of poison, but > that's not the kernel's fault, that's the hardware. What happens when > hardware really does detect 8 blocks of consective poison and this > implementation decides to only record 1 at a time?
In that case, there will be 8 reports of the poisons by APEI GHES, and ARC scan will also report 8 poisons, each will get to be added to the bad range via nvdimm_bus_add_badrange(), so none of them will be missed.
In the above 2 poison example, the poison in 0x00000040a0602400 and in 0x00000040a0602600 were separately reported.
> > It seems the fix you want is for the hardware to report the precise > error bounds and that 1UL << MCI_MISC_ADDR_LSB(mce->misc) does not have > that precision in this case.
That field describes a 4K range even for a single poison, it confuses people unnecessarily.
> > However, the ARS engine likely can return the precise error ranges so I > think the fix is to just use the address range indicated by 1UL << > MCI_MISC_ADDR_LSB(mce->misc) to filter the results from a short ARS > scrub request to ask the device for the precise error list.
You mean for nfit_handle_mce() callback to issue a short ARS per each poison report over a 4K range in order to decide the precise range as a workaround of the hardware issue? if there are 8 poisoned detected, there will be 8 short ARS, sure we want to do that? also, for now, is it possible to log more than 1 poison per 512byte block?
thanks! -jane
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