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).
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.
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
206     Indicates the shadow page is created for a nested guest.
228     at the shadow page structure.
229     sptes in spt point either at guest pages, or at lower-level shadow pages.
230     Specifically, if sp1 and sp2 are shadow pages, then sp1->spt[n] may point
232     The spt array forms a DAG structure with the shadow page as a node, and
235     An array of 512 shadow translation entries, one for each present pte. Used
243      root_count is a reference counter for root shadow pages in Shadow MMU.
244      vCPUs elevate the refcount when getting a shadow page that will be used as
256     The kernel virtual address of the SPTE that points at this shadow page.
286     Is 1 if the shadow page is a TDP MMU page. This variable is used to
288     may contain pages from both TDP MMU and shadow MMU.
315 As a side effect we have to resynchronize all reachable unsynchronized shadow
330     - synchronized shadow pages are write protected (*)
340    - walk shadow page table
360  - walk the shadow page table to find the spte for the translation,
378   - walk the shadow page hierarchy and drop affected translations
386   - look up new shadow roots
387   - synchronize newly reachable shadow pages
392   - look up new shadow roots
393   - synchronize newly reachable shadow pages
426   shadow paging is in use.
429   CR4.SMAP && !CR0.WP into shadow page's role to avoid this case. Note,
437 it will simply be missed by the shadow page lookup code.  A similar issue
472 shadow pages, and is made more scalable with a similar technique.