It's most likely a callback from OS to firmware, or at least this is what I can guess based on the single comment present in the screenshot and what I saw in the past in the APEI tables of Intel-based servers.
APEI tables are a part of ACPI that tell the OS how to write an error record persistently in the machine log, inject a memory error for debugging purposes, and stuff like that that's tied to the RAS (Reliability/Availability/Serviceability) features of a server. The tables contain a list of instructions like "write a value to memory" or "write a value to an I/O port"; the way they work in practice is that, by following these instructions, the OS causes the processor to enter system management mode (that's the "backdoor" into the firmware) where the firmware services the APEI request.
Since the tweet mentions SMM and RAS in the two lines it shows, my guess is that it's related to that functionality.
bonzini|5 years ago
APEI tables are a part of ACPI that tell the OS how to write an error record persistently in the machine log, inject a memory error for debugging purposes, and stuff like that that's tied to the RAS (Reliability/Availability/Serviceability) features of a server. The tables contain a list of instructions like "write a value to memory" or "write a value to an I/O port"; the way they work in practice is that, by following these instructions, the OS causes the processor to enter system management mode (that's the "backdoor" into the firmware) where the firmware services the APEI request.
Since the tweet mentions SMM and RAS in the two lines it shows, my guess is that it's related to that functionality.
unknown|5 years ago
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