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KVM: Documentation: Add the missing description for tdp_mmu_root_count into kvm_mmu_page

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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@google.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20230912184553.1887764-5-mizhang@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Mingwei Zhang 2023-09-12 18:45:51 +00:00 committed by Sean Christopherson
parent b40a2455e9
commit 6a713928ae
1 changed files with 7 additions and 4 deletions
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11
Documentation/virt/kvm/x86/mmu.rst
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@ -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