linux-kernel - Re: [PATCH 5/6] KVM: Documentation: Add the missing mmu_valid_gen into kvm_mmu

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Date:   Thu, 22 Jun 2023 08:42:32 +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>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "dmatlack@...gle.com" <dmatlack@...gle.com>,
        "bgardon@...gle.com" <bgardon@...gle.com>
Subject: Re: [PATCH 5/6] KVM: Documentation: Add the missing mmu_valid_gen
 into kvm_mmu_page

On Sun, 2023-06-18 at 00:08 +0000, Mingwei Zhang wrote:
> Add mmu_valid_gen into kvm_mmu_page description. mmu_valid_gen is used in
> shadow MMU for fast zapping. Update the doc to reflect that.
> 
> Signed-off-by: Mingwei Zhang <mizhang@...gle.com>
> ---
>  Documentation/virt/kvm/x86/mmu.rst | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/Documentation/virt/kvm/x86/mmu.rst b/Documentation/virt/kvm/x86/mmu.rst
> index 3dce2426ad6d..0dbdb7fb8cc6 100644
> --- a/Documentation/virt/kvm/x86/mmu.rst
> +++ b/Documentation/virt/kvm/x86/mmu.rst
> @@ -208,6 +208,10 @@ Shadow pages contain the following information:
>      The page is not backed by a guest page table, but its first entry
>      points to one.  This is set if NPT uses 5-level page tables (host
>      CR4.LA57=1) and is shadowing L1's 4-level NPT (L1 CR4.LA57=1).
> +  mmu_valid_gen:
> +    Used by comparing against kvm->arch.mmu_valid_gen to check whether the
> +    shadow page is obsolete thus a convenient variable for fast zapping.
> +    Note that TDP MMU does not use mmu_valid_gen.
>    gfn:
>      Either the guest page table containing the translations shadowed by this
>      page, or the base page frame for linear translations.  See role.direct.

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