linux-kernel - Re: [PATCH v13 07/35] KVM: Convert KVM_ARCH_WANT_MMU_NOTIFIER to CONFIG_KVM_GENERIC_MMU

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Message-ID: <09966596-397a-47c6-8f43-610a1013d34a@redhat.com>
Date:   Mon, 30 Oct 2023 17:37:42 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        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>
Cc:     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 07/35] KVM: Convert KVM_ARCH_WANT_MMU_NOTIFIER to
 CONFIG_KVM_GENERIC_MMU_NOTIFIER

On 10/27/23 20:21, Sean Christopherson wrote:
> Convert KVM_ARCH_WANT_MMU_NOTIFIER into a Kconfig and select it where
> appropriate to effectively maintain existing behavior.  Using a proper
> Kconfig will simplify building more functionality on top of KVM's
> mmu_notifier infrastructure.
> 
> Add a forward declaration of kvm_gfn_range to kvm_types.h so that
> including arch/powerpc/include/asm/kvm_ppc.h's with CONFIG_KVM=n doesn't
> generate warnings due to kvm_gfn_range being undeclared.  PPC defines
> hooks for PR vs. HV without guarding them via #ifdeffery, e.g.
> 
>   bool (*unmap_gfn_range)(struct kvm *kvm, struct kvm_gfn_range *range);
>   bool (*age_gfn)(struct kvm *kvm, struct kvm_gfn_range *range);
>   bool (*test_age_gfn)(struct kvm *kvm, struct kvm_gfn_range *range);
>   bool (*set_spte_gfn)(struct kvm *kvm, struct kvm_gfn_range *range);
> 
> Alternatively, PPC could forward declare kvm_gfn_range, but there's no
> good reason not to define it in common KVM.

The new #define should also imply KVM_CAP_SYNC_MMU, or even: 
KVM_CAP_SYNC_MMU should just be enabled by all architectures at this 
point.  You don't need to care about it, I have a larger series for caps 
that are enabled by all architectures and I'll post it for 6.8.

Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>

Paolo