On Sun, May 27, 2018 at 08:45:53AM -0700, Fenghua Yu wrote: > set_bit() called by set_cpu_cap() is a locked bit set instruction for > atomic operation. > > Since the c->x86_capability can span two cache lines depending on kernel > configuration and building evnironment, the locked bit set instruction may > cause #AC exception when #AC exception for split lock is enabled.
That doesn't make sense. Sure the bitmap may be longer, but depending on if the argument is an immediate or not we either use a byte instruction (which can never cross a cacheline boundary) or a 'word' aligned BTS. And the bitmap really _should_ be 'unsigned long' aligned. If it is not aligned, fix that too. /me looks at cpuinfo_x86 and finds x86_capability is in fact a __u32 array.. see that's broken and needs fixing first.
