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Tony Luck authored
Reading machine check bank registers is slow. There is a trend of increasing the number of banks, and the number of cores. The main section of do_machine_check() is a serialized section where each cpu in turn checks every bank. Even on a little two socket SandyBridge-EP system that multiplies out as: 2 sockets * 8 cores * 2 hyperthreads * 20 banks = 640 MSRs We already scan the banks in parallel in mce_no_way_out() to see if there is a fatal error anywhere in the system. If we build a cache of VALID bits during this scan, we can avoid uselessly re-reading banks that have no data. Note that this cache is only a hint. If the valid bit is set in a shared bank, all cpus that share that bank will see it during the parallel scan, but the first to find it in the sequential scan will (usually) clear the bank. Acked-by: Borislav Petkov <borislav.petkov@amd.com> Signed-off-by: Tony Luck <tony.luck@intel.com>
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