* Flushing user entries for kernel mappings in x86
@ 2018-08-29 1:46 Nadav Amit
2018-08-29 3:45 ` Andy Lutomirski
0 siblings, 1 reply; 3+ messages in thread
From: Nadav Amit @ 2018-08-29 1:46 UTC (permalink / raw)
To: Andy Lutomirski; +Cc: Linux Kernel Mailing List
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 ].
Thanks,
Nadav
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Flushing user entries for kernel mappings in x86
2018-08-29 1:46 Flushing user entries for kernel mappings in x86 Nadav Amit
@ 2018-08-29 3:45 ` Andy Lutomirski
2018-08-29 8:37 ` Nadav Amit
0 siblings, 1 reply; 3+ messages in thread
From: Andy Lutomirski @ 2018-08-29 3:45 UTC (permalink / raw)
To: Nadav Amit; +Cc: Andy Lutomirski, Linux Kernel Mailing List
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.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Flushing user entries for kernel mappings in x86
2018-08-29 3:45 ` Andy Lutomirski
@ 2018-08-29 8:37 ` Nadav Amit
0 siblings, 0 replies; 3+ messages in thread
From: Nadav Amit @ 2018-08-29 8:37 UTC (permalink / raw)
To: Andy Lutomirski; +Cc: Linux Kernel Mailing List
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.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2018-08-29 1:46 Flushing user entries for kernel mappings in x86 Nadav Amit
2018-08-29 3:45 ` Andy Lutomirski
2018-08-29 8:37 ` Nadav Amit
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