On 07/12/2016 03:55 PM, H. Peter Anvin wrote: > On 07/12/16 08:32, Dave Hansen wrote: >> On 07/09/2016 02:27 PM, Andy Lutomirski wrote: >>> is_prefetch in arch/x86/mm/fault.c can be called on a user address >>> that's not readable due to PKRU. This could break it. You might need >>> to add a get_user_exec or similar. >> >> Thanks for the heads-up. I think I'll just need a version that does >> something along the lines of stac/clac, but with PKRU. >> >> I think I can do it with an "_exec" variant of probe_kernel_address(), >> but it's a bit messy. > > Can this particular codepath even be executed on a PKRU-equipped > machine? I thought it was a bug fix for a specific AMD CPU line.
Yeah, I think we hit it unconditionally in the naughty paths of the page fault handler. I don't see any CPU model detection in the call path. I think we just assume that everybody has prefetch bugs.
