On Thu, Dec 20, 2018 at 12:36:35AM -0700, Jan Beulich wrote:
> >>> On 19.12.18 at 13:54, <jbeul...@suse.com> wrote:
> >>>> On 19.12.18 at 12:55, <bou...@antioche.eu.org> wrote:
> >> On Wed, Dec 19, 2018 at 04:05:57AM -0700, Jan Beulich wrote:
> >>> In any event, both Andrew and I must have overlooked the one
> >>> crucial place due to which the assertion is indeed wrong from
> >>> put_page_from_l2e():
> >>>
> >>> int rc = _put_page_type(pg, false, mfn_to_page(_mfn(pfn)));
> >>>
> >>> Not allowing for preemption there is fine if the L2E is pointing to
> >>> an L1 table, but is now wrong if the L2E points to another L2,
> >>> which surely is the case when you see the assertion trigger.
> >>
> >> Should we just change false to true here, or should the cases above be
> >> handled differently ?
> >
> > Switching from false to true here is just the initial part of the
> > necessary change - if you did just this, you'd end up hitting
> > the ASSERT() right after the line above. There's quite a bit
> > more to it, and it needs to be done pretty carefully.
>
> Actually there was no reason to alter the free_l2_table() paths
> in the XSA-273 fixes: A switch to shadow mode can only occur
> when validating page tables. Therefore I think you could safely
> revert the respective hunks, which includes deleting the
> ASSERT() you found triggering.
You mean, Xen is not going to fix this ?
--
Manuel Bouyer <bou...@antioche.eu.org>
NetBSD: 26 ans d'experience feront toujours la difference
--
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