Messages in this thread | | | Date | Fri, 02 Mar 2012 13:02:13 +0900 | From | Hidetoshi Seto <> | Subject | Re: [PATCH 1/3] mce: Add a msg string to the MCE tracepoint |
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(2012/03/02 3:28), Luck, Tony wrote: >>> My concern is; on Sandy Bridge, is it safe to gather info about the DIMM >>> location in/from machine check context in a reasonable time span? >> >> Well, what amd64_edac does is "buffer" the required lookup info so >> whenever you get an error, you simply lookup the channel and chip select >> - all ops which can be done in atomic context. > > Yes - we could pre-read all the config space registers ahead of time and > save them in memory (none of the values should change - except if the platform > supports hot-plug for memory). Total is only a few Kbytes. Then decode in > machine check context is both safe, and fast.
To sort out my thought:
- First of all, OS gathers info about physical location of DIMMs from DMI/ACPI/PCI etc., before enabling MCE mechanism. - Make a kind of "physical memory location table" on memory buffer, to ease mapping a physical address to the location of a DIMM module and/or chip which have the memory cell pointed by the address. - It would be better to have a well organized table rather than having a raw copy of config space etc. - Likewise it will also nice if we can map logical processor numbers to the location of physical sockets on motherboard. - Happy if user can refer the table via sysfs. - Allow updating the table if the platform supports hot-plug. - Once MCE is enabled, handler can refer the table on memory to determine an erroneous device which should be replaced.
This storyline up to here is reasonable and acceptable, I think.
Then now it is clear that the last point where I feel uneasy about is putting a string into the ring buffer instead of binary bits like index of location table. Please use binary (or "binary + string") to tell the error location to userland.
Thanks, H.Seto
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