CVE-2023-34322

For migration as well as to work around kernels unaware of L1TF (see
XSA-273), PV guests may be run in shadow paging mode. Since Xen itself
needs to be mapped when PV guests run, Xen and shadowed PV guests run
directly the respective shadow page tables. For 64-bit PV guests this means
running on the shadow of the guest root page table. In the course of
dealing with shortage of memory in the shadow pool associated with a
domain, shadows of page tables may be torn down. This tearing down may
include the shadow root page table that the CPU in question is presently
running on. While a precaution exists to supposedly prevent the tearing
down of the underlying live page table, the time window covered by that
precaution isn’t large enough.

Notes