[Bug 210695] error: kvm run failed Invalid argument

[bugzilla-daemon@bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=210695

--- Comment #7 from Sean Christopherson (seanjc@google.com) ---
Finally figured it out.  When KVM uses PAE shadow paging, the PDPTRs are
effectively skipped when walking the shadow tables because a bad PDPTR will be
detected much earlier and KVM essentially hardcodes the PDPTRs.  As a result,
the corresponding SPTE isn't filled by get_walk() as it never "sees" the SPTE
for the PDTPR.  The refactored get_mmio_spte() doesn't account for this and
checks the PDPTR SPTE array value.  This reads uninitialized stack data, and in
your case, this yields the garbage value '0x80000b0e' that causes things to
explode (my system gets '0' most/all of the time).

I'll get a patch out later today, it's a bit of a mess....

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