linux-kernel - Re: [RFC PATCH v2 41/69] KVM: x86: Add infrastructure for stolen GPA bits

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Message-ID: <YQ2zH+XiLCLQWs0l@google.com>
Date:   Fri, 6 Aug 2021 22:09:35 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Kai Huang <kai.huang@...el.com>
Cc:     isaku.yamahata@...el.com, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, erdemaktas@...gle.com,
        Connor Kuehl <ckuehl@...hat.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        isaku.yamahata@...il.com,
        Rick Edgecombe <rick.p.edgecombe@...el.com>
Subject: Re: [RFC PATCH v2 41/69] KVM: x86: Add infrastructure for stolen GPA
 bits

On Sat, Aug 07, 2021, Kai Huang wrote:
> So could we have your final suggestion? :)

Try the kvm_mmu_page_role.private approach.  So long as it doesn't end up splattering
code everywhere, I think that's more aligned with how KVM generally wants to treat
the shared bit.

In the changelog for this patch, make it very clear that ensuring different aliases
get different shadow page (if necessary) is the responsiblity of each individual
feature that leverages stolen gfn bits.