Re: [RFC PATCH v2 12/27] x86/mm: Shadow stack page fault error checking

[Dave Hansen]

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?