On 07/10/2018 03:26 PM, Yu-cheng Yu wrote: > +++ b/arch/x86/include/asm/traps.h > @@ -157,6 +157,7 @@ enum { > * bit 3 == 1: use of reserved bit detected > * bit 4 == 1: fault was an instruction fetch > * bit 5 == 1: protection keys block access > + * bit 6 == 1: shadow stack access fault > */ Could we document this bit better? Is this a fault where the *processor* thought it should be a shadow stack fault? Or is it also set on faults to valid shadow stack PTEs that just happen to fault for other reasons, say protection keys?