linux-kernel - Re: [PATCH v13 12/35] KVM: Prepare for handling only shared mappings in mmu

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Message-ID: <cbd46f04-c53b-4d22-9730-76f2ace141d9@redhat.com>
Date:   Thu, 2 Nov 2023 12:14:13 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Binbin Wu <binbin.wu@...ux.intel.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     Marc Zyngier <maz@...nel.org>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Huacai Chen <chenhuacai@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Anup Patel <anup@...infault.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>, kvm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        linux-mips@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        kvm-riscv@...ts.infradead.org, linux-riscv@...ts.infradead.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Xiaoyao Li <xiaoyao.li@...el.com>,
        Xu Yilun <yilun.xu@...el.com>,
        Chao Peng <chao.p.peng@...ux.intel.com>,
        Fuad Tabba <tabba@...gle.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Anish Moorthy <amoorthy@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        Isaku Yamahata <isaku.yamahata@...el.com>,
        Mickaël Salaün <mic@...ikod.net>,
        Vlastimil Babka <vbabka@...e.cz>,
        Vishal Annapurve <vannapurve@...gle.com>,
        Ackerley Tng <ackerleytng@...gle.com>,
        Maciej Szmigiero <mail@...iej.szmigiero.name>,
        David Hildenbrand <david@...hat.com>,
        Quentin Perret <qperret@...gle.com>,
        Michael Roth <michael.roth@....com>,
        Wang <wei.w.wang@...el.com>,
        Liam Merwick <liam.merwick@...cle.com>,
        Isaku Yamahata <isaku.yamahata@...il.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH v13 12/35] KVM: Prepare for handling only shared mappings
 in mmu_notifier events

On 11/2/23 06:59, Binbin Wu wrote:
> 
>> Add flags to "struct kvm_gfn_range" to let notifier events target
>> only shared and only private mappings, and write up the existing
>> mmu_notifier events to be shared-only (private memory is never
>> associated with a userspace virtual address, i.e. can't be reached
>> via mmu_notifiers).
>> 
>> Add two flags so that KVM can handle the three possibilities
>> (shared, private, and shared+private) without needing something
>> like a tri-state enum.
>
> I see the two flags are set/cleared in __kvm_handle_hva_range() in
> this patch and kvm_handle_gfn_range() from the later patch 13/35, but
> I didn't see they are used/read in this patch series if I didn't miss
> anything.  How are they supposed to be used in KVM?

They are going to be used by SNP/TDX patches.

Paolo