kvm/x86/mmu.rst

4 The x86 kvm shadow mmu
55 spte  shadow pte (referring to pfns)
87 direct mode; otherwise it operates in shadow mode (see below).
118 Shadow pages
121 The principal data structure is the shadow page, 'struct kvm_mmu_page'.  A
122 shadow page contains 512 sptes, which can be either leaf or nonleaf sptes.  A
123 shadow page may contain a mix of leaf and nonleaf sptes.
126 is not related to a translation directly.  It points to other shadow pages.
150 Shadow pages contain the following information:
152     The level in the shadow paging hierarchy that this shadow page belongs to.
166     so multiple shadow pages are needed to shadow one guest page.
167     For first-level shadow pages, role.quadrant can be 0 or 1 and denotes the
171     shadow pages) so role.quadrant takes values in the range 0..3.  Each
198     shadow page; it is also used to go back from a struct kvm_mmu_page
203     bits before Haswell; shadow EPT page tables also cannot use A/D bits
216     at the shadow page structure.
217     sptes in spt point either at guest pages, or at lower-level shadow pages.
218     Specifically, if sp1 and sp2 are shadow pages, then sp1->spt[n] may point
220     The spt array forms a DAG structure with the shadow page as a node, and
290 As a side effect we have to resynchronize all reachable unsynchronized shadow
305     - synchronized shadow pages are write protected (*)
315    - walk shadow page table
335  - walk the shadow page table to find the spte for the translation,
353   - walk the shadow page hierarchy and drop affected translations
361   - look up new shadow roots
362   - synchronize newly reachable shadow pages
367   - look up new shadow roots
368   - synchronize newly reachable shadow pages
401   shadow paging is in use.
404   CR4.SMAP && !CR0.WP into shadow page's role to avoid this case. Note,
412 it will simply be missed by the shadow page lookup code.  A similar issue
447 shadow pages, and is made more scalable with a similar technique.