Add the description of tdp_mmu_root_count into kvm_mmu_page description and
combine it with the description of root_count. tdp_mmu_root_count is an
atomic counter used only in TDP MMU. Update the doc.
Signed-off-by: Mingwei Zhang <mizhang@xxxxxxxxxx>
Reviewed-by: Kai Huang <kai.huang@xxxxxxxxx>
---
Documentation/virt/kvm/x86/mmu.rst | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/Documentation/virt/kvm/x86/mmu.rst b/Documentation/virt/kvm/x86/mmu.rst
index 22d221c180d7..4a82fa016833 100644
--- a/Documentation/virt/kvm/x86/mmu.rst
+++ b/Documentation/virt/kvm/x86/mmu.rst
@@ -229,10 +229,13 @@ Shadow pages contain the following information:
can be calculated from the gfn field when used. In addition, when
role.direct is set, KVM does not track access permission for each of the
gfn. See role.direct and gfn.
- root_count:
- A counter keeping track of how many hardware registers (guest cr3 or
- pdptrs) are now pointing at the page. While this counter is nonzero, the
- page cannot be destroyed. See role.invalid.
+ root_count / tdp_mmu_root_count:
+ root_count is a reference counter for root shadow pages in Shadow MMU.
+ vCPUs elevate the refcount when getting a shadow page that will be used as
+ a root page, i.e. page that will be loaded into hardware directly (CR3,
+ PDPTRs, nCR3 EPTP). Root pages cannot be destroyed while their refcount is
+ non-zero. See role.invalid. tdp_mmu_root_count is similar but exclusively
+ used in TDP MMU as an atomic refcount.
parent_ptes:
The reverse mapping for the pte/ptes pointing at this page's spt. If
parent_ptes bit 0 is zero, only one spte points at this page and
--
2.42.0.283.g2d96d420d3-goog
