linux-kernel - Re: [PATCH V2 4/7] KVM: X86/MMU: Activate special shadow pages and remove old logic

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Message-ID: <CAJhGHyDS0NXmcW99rtvxp3YTGFcD_eOxRs+_3caUN6ki6z1BuA@mail.gmail.com>
Date:   Thu, 26 May 2022 17:15:12 +0800
From:   Lai Jiangshan <jiangshanlai@...il.com>
To:     David Matlack <dmatlack@...gle.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        "open list:KERNEL VIRTUAL MACHINE FOR MIPS (KVM/mips)" 
        <kvm@...r.kernel.org>, Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Lai Jiangshan <jiangshan.ljs@...group.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        X86 ML <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH V2 4/7] KVM: X86/MMU: Activate special shadow pages and
 remove old logic

On Tue, May 17, 2022 at 8:16 AM David Matlack <dmatlack@...gle.com> wrote:

>
> This comment does not explain why FNAME(fetch) might pass these values
> to allocate special shadow pages. How about adjust it to something like
> this:
>
>   /*
>    * Initialize the guest walker with default values.  These values will
>    * be used in cases where KVM shadows a guest page table structure
>    * with more levels than what the guest. For example, KVM shadows
>    * 2-level non-PAE guests with 3-level PAE paging.
>    *
>    * Note, the gfn is technically ignored for these special shadow
>    * pages, but it's more consistent to always pass 0 to
>    * kvm_mmu_get_page().
>    */

The comment is copied into V3 with slightly changed.

>
> > +     for (i = 2; i < PT_MAX_FULL_LEVELS; i++) {
>
> s/2/PT32_ROOT_LEVEL/
>

Did in v3

Thanks
Lai