Hi, I'd like to report a regression which seems related to the latest ITS mitigations in Linux 6.1.x:
The server in question is a Supermicro SYS-120C-TN10R with a "Intel(R) Xeon(R) Silver 4310 CPU @ 2.10GHz" CPU, running Debian Bookworm. The full output of /proc/cpuinfo is attached as cpuinfo.txt
In addition to the kernel changes between 6.1.135 and 6.1.139 there is also some additional invariant, namely the Intel microcode loaded at early boot:
On Linux 6.1.135 every works fine with both the 20250211 and 20250512 microcode releases (kern.log is attached as 6.1.135-feb-microcode.log and 6.1.135-may-microcode.log)
With 6.1.139 and the February microcode, oopses appear related to clear_bhb_loop() (which may be related to "x86/its: Align RETs in BHB clear sequence to avoid thunking"?). This is captured in 6.1.139-feb-microcode.log.
With 6.1.139 and the May microcode, the system mostly crashes on bootup (in my tests it crashed in three out of four attempts). I've captured both the crash (6.1.139-may-microcode-crash.log) and a working boot (6.1.139-may-microcode-noncrash.log).
If you need any additional information, please let me know!
Cheers, Moritz