linux-kernel - Re: [PATCH v2 4/6] KVM: Documentation: Add the missing description for tdp_mmu_root_count into kvm_mmu

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Message-ID: <5a6fb38bb223516bdf3da0378dbfa89be8b62f6f.camel@intel.com>
Date:   Mon, 26 Jun 2023 22:21:42 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "mizhang@...gle.com" <mizhang@...gle.com>
CC:     "jmattson@...gle.com" <jmattson@...gle.com>,
        "Xu, Yilun" <yilun.xu@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "dmatlack@...gle.com" <dmatlack@...gle.com>,
        "zhi.wang.linux@...il.com" <zhi.wang.linux@...il.com>,
        "bgardon@...gle.com" <bgardon@...gle.com>
Subject: Re: [PATCH v2 4/6] KVM: Documentation: Add the missing description
 for tdp_mmu_root_count into kvm_mmu_page

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@...gle.com>
> ---
>  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@...el.com>