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Two Months After Being Merged, Intel In-Field Scan Marked "Broken" For Linux 5.19
Sent in today were a final set of planned platform-drivers-x86 fixes for the Linux 5.19 kernel. There are some common fixes as well as hardware ID additions (including for a new AMD platform), but most notable is that the Intel IFS driver is being marked as "BROKEN".
Intel In-Field Scan (IFS) is the Linux driver for a new hardware feature being introduced with Xeon Sapphire Rapids. Intel In-Field Scan is a hardware silicon testing feature for loading binaries of tests to vet particular silicon either prior to deployment in production and/or over time as the hardware is aging for trying to catch any issues. The IFS tests are silicon-level tests designed to catch hardware issues not caught by existing MCE or ECC errors.
Intel's description of In-Field Scan.
In-Field Scan should help spot faulty silicon and particularly useful for large hyperscalers. The Linux driver allows loading of these tests for execution on the given CPU and for reporting any errors.
While the IFS driver was merged to mainline back in late May as part of the Linux 5.19 merge window, it's now been determined that there are some issues surrounding its user-space API that need to be cleared up.
In particular, the current IFS driver implementation with its sysfs interface only allows IFS images to be loaded using a default file-name of ff-mm-ss.scan. Intel earlier this month proposed patches to change the behavior of the driver's sysfs reload file where it would support loading alternative filenames from within the /lib/firmware/intel/ifs directory. Intel engineers are wanting this change to support increased test coverage, custom test files to debug particular issues in-field, etc.
But changing their sysfs interface could break their user-space interface and that's a big no-no, as also shown with their Intel GuC firmware handling for ADL-P in Linux 5.19. The x86 platform driver maintainer Hans de Goede has thus marked the IFS driver as "BROKEN" until ensuring the user-space API is right. So the code can still be built with the upcoming Linux 5.19 but users are then very aware of the "broken" state with its sysfs interface possibly subject to change in Linux 5.20. Changes that affect their user-space interface should be addressed prior to mainlining/upstreaming the driver in the Linux kernel as to not break user workflows.
The full list of platform-drivers-x86 changes submitted today for Linux 5.19 can be found via this pull request.