Re: [Xen-devel] 4.11.0 RC1 panic

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 10.06.18 at 18:32, <bouyer@xxxxxxxxxxxxxxx> wrote:
> On Sun, Jun 10, 2018 at 09:38:17AM -0600, Jan Beulich wrote:
>> What about L2 tables to be used in slot 3 of an L3 table? Aiui Xen won't 
>> allow
>> them to be pinned, hence I'd expect there to be some special casing in your
>> code. Considering no similar issues have been observed with 64-bit guests,
>> this one special case looks to me to be the prime suspect for something going
>> wrong (in Xen).
> 
> AFAIK this L2 is allocated at boot, and should never be freed. It's
> shared by all CPUs.

I guess that's what goes into L3 slot 3 and ...

> There is one special L2 case: it's pinned as L2 but used as L1 in the "kernel"
> L2 (the one in slot 3 of the L3 tables). This is for recursive mappings
> of the kernel map. This one will be allocated/freed (and so pinned/unpinned)
> for each context.

... here you mean L3 slot 2 (all assuming 0-based slot numbering)?
Otherwise I'm afraid I'm confused now, as the sharing by all CPUs of
the former seems to contradict the per-context nature of the latter.

Jan



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