From 6a713928ae1cb8aaa008b6ffb709fd9293614c89 Mon Sep 17 00:00:00 2001 From: Mingwei Zhang Date: Tue, 12 Sep 2023 18:45:51 +0000 Subject: [PATCH] KVM: Documentation: Add the missing description for tdp_mmu_root_count into kvm_mmu_page 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 Reviewed-by: Kai Huang Link: https://lore.kernel.org/r/20230912184553.1887764-5-mizhang@google.com Signed-off-by: Sean Christopherson --- 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 d5b08b4e8ff1..55d72383f6d6 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