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SubjectRe: [RFC PATCH 5/7] x86/mm/fault: hook up SCI verification
On Fri, Apr 26, 2019 at 09:42:23AM +0200, Peter Zijlstra wrote:
> On Fri, Apr 26, 2019 at 12:45:52AM +0300, Mike Rapoport wrote:
> > If a system call runs in isolated context, it's accesses to kernel code and
> > data will be verified by SCI susbsytem.
> >
> > Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
> > ---
> > arch/x86/mm/fault.c | 28 ++++++++++++++++++++++++++++
> > 1 file changed, 28 insertions(+)
>
> There's a distinct lack of touching do_double_fault(). It appears to me
> that you'll instantly trigger #DF when you #PF, because the #PF handler
> itself will not be able to run.

The #PF handler is able to run. On interrupt/error entry the cr3 is
switched to the full kernel page tables, pretty much like PTI does for
user <-> kernel transitions. It's in the patch 3.

> And then obviously you have to be very careful to make sure #DF can,
> _at_all_times_ run, otherwise you'll tripple-fault and we all know what
> that does.
>

--
Sincerely yours,
Mike.

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