Re: Flushing user entries for kernel mappings in x86

From: Andy Lutomirski
Date: Tue Aug 28 2018 - 23:45:48 EST

On Tue, Aug 28, 2018 at 6:46 PM, Nadav Amit <nadav.amit@xxxxxxxxx> wrote:
> Hello Andy,
> Is there a reason for __flush_tlb_one_kernel() to flush the PTE not only in
> the kernel address space, but also in the user one (as part of
> __flush_tlb_one_user)? [ I obviously regard the case when PTI is on ].

In most cases, probably not, but it's fairly cheap, I think. And it
makes it so that we're okay if the TLB entry we're flushing is used by
the entry code.