On 10/25/21 3:59 AM, Peter Zijlstra wrote:

quoted

Add a check to prevent access_error() from returning mistakenly that
page-faults due to instruction fetch are not allowed. Intel SDM does not
indicate whether "instruction fetch" and "write" in the hardware error
code are mutual exclusive, so check both before returning whether the
access is allowed.

Dave, can we get that clarified? It seems a bit naf and leads to
confusing code IMO.

We can, but there are quite a few implicit relationships in those bits.
 PF_INSN and PF_PK can't ever be set together, for instance.  It's
pretty clear as long as you have fetch==read in your head.