Re: [PATCH v2 4/6] KVM: Documentation: Add the missing description for tdp_mmu_root_count into kvm_mmu_page

[Huang, Kai]

On Mon, 2023-06-26 at 18:20 +0000, Mingwei Zhang wrote:
> Add the description of tdp_mmu_root_count into kvm_mmu_page description.
> tdp_mmu_root_count is an atomic counter used only in TDP MMU. Its usage and
> meaning is slightly different with root_counter in shadow MMU. Update the
> doc.
> 
> Signed-off-by: Mingwei Zhang <mizhang@xxxxxxxxxx>
> ---
>  Documentation/virt/kvm/x86/mmu.rst | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/Documentation/virt/kvm/x86/mmu.rst b/Documentation/virt/kvm/x86/mmu.rst
> index 5cd6cd5e8926..97d695207e11 100644
> --- a/Documentation/virt/kvm/x86/mmu.rst
> +++ b/Documentation/virt/kvm/x86/mmu.rst
> @@ -231,6 +231,11 @@ Shadow pages contain the following information:
>      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.
> +  tdp_mmu_root_count:
> +    An atomic reference counter in TDP MMU root page that allows for parallel
> +    accesses.  Accessing the page requires lifting the counter value. The
> +    initial value is set to 2 indicating one reference from vCPU and one
> +    from TDP MMU itself. Note this field is a union with root_count.
>    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
> -- 
> 2.41.0.162.gfafddb0af9-goog
> 

Reviewed-by: Kai Huang <kai.huang@xxxxxxxxx>