Re: [Xen-devel] [TESTDAY] Test report

[Jürgen Groß <jgross@xxxxxxxx>]

On 15.11.19 16:19, Tamas K Lengyel wrote:
> On Fri, Nov 15, 2019 at 4:56 AM Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
> > On 14/11/2019 22:36, Tamas K Lengyel wrote:
> > > On Thu, Nov 14, 2019 at 11:39 AM Andrew Cooper
> > > <andrew.cooper3@xxxxxxxxxx> wrote:
> > > > On 14/11/2019 18:34, Tamas K Lengyel wrote:
> > > > > * Comments: All works, altp2m+introspection requires the ept=pml=0
> > > > > boot flag specified to workaround a deadlock in Xen
> > > > Is this separate from the general problem with EPT A/D and
> > > > write-protecting pagetables?
> > > It sounds like it is, it happens without write-protecting in-guest
> > > pagetables. I didn't have time to investigate where the deadlock
> > > happens and since the workaround is fine for the usecase it wasn't a
> > > priority to figure out.
> > Thinking about it, PML will do the wrong thing (deadlocks aside) as soon
> > as any altp2m gfn translations are used.
> >
> > I'd be tempted to work around the deadlock by disabling pml the moment
> > altp2m is touched.  That would give a sightly less bad user experience,
> > and should be easy to sort for 4.13.
> >
> > Thoughts, (inc. Juergen as RM) ?
> That sounds like a good idea to me, that way you can keep pml for
> guests where it doesn't cause an issue instead of disabling it system
> wide.
Sounds like decent way to handle it.


Juergen


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