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

Huang, Kai
2023-06-22T08:37:39Z

On Sun, 2023-06-18 at 00:08 +0000, Mingwei Zhang wrote:
> Add 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@google.com>
> ---
> Documentation/virt/kvm/x86/mmu.rst | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/Documentation/virt/kvm/x86/mmu.rst b/Documentation/virt/kvm/x86/mmu.rst
> index 36bfe0fe02bb..3dce2426ad6d 100644
> --- a/Documentation/virt/kvm/x86/mmu.rst
> +++ b/Documentation/virt/kvm/x86/mmu.rst
> @@ -230,6 +230,12 @@ 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 that allows for parallel
^
Please explicitly say "TDP MMU root page" ?

> + accesses. Accessing the page requires lifting the counter value. The
> + initial value is set as 2 indicating one reference from vCPU and one
^
to ?

> + from TDP MMU itself.
>

> While this counter is nonzero, the page cannot be
> + destroyed.
>

I guess this sentence is implied by "reference counter" mentioned in the first
sentence.

> Note this field is a union with root_count.
>