Re: [PATCH] x86/mm/pti: in pti_clone_pgtable() don't increase addr by PUD_SIZE

On 8/20/19 7:14 AM, Song Liu wrote:

...

*But*, that shouldn't get hit on a Skylake CPU since those have PCIDs and shouldn't have a global kernel image. Could you confirm whether PCIDs are supported on this CPU?

Yes, pcid is listed in /proc/cpuinfo.

So what's going on? Could you confirm exactly which pti_clone_pgtable() is causing you problems? Do you have a theory as to why this manifests as a performance problem rather than a functional one?

A diff of these:

/sys/kernel/debug/page_tables/current_user /sys/kernel/debug/page_tables/current_kernel

before and after your patch might be helpful.