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SubjectRe: Flushing user entries for kernel mappings in x86
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at 8:45 PM, Andy Lutomirski <luto@kernel.org> wrote:

> On Tue, Aug 28, 2018 at 6:46 PM, Nadav Amit <nadav.amit@gmail.com> 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.

Thanks. I assumed that’s the case. I don’t know how cheap they are
(especially if INVPCID is not supported) but I guess they are not that
frequent.

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