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From:   David Matlack <dmatlack@google.com>
Date:   Mon, 30 Oct 2023 11:21:12 -0700
Message-ID: <CALzav=djOS8T7AmUa3A7QmP1f0xAm2W-KRDmOov_H8ps77A2qA@mail.gmail.com>
Subject: Re: [PATCH v13 03/35] KVM: Use gfn instead of hva for mmu_notifier_retry
To:     Paolo Bonzini <pbonzini@redhat.com>
Cc:     Sean Christopherson <seanjc@google.com>,
        Marc Zyngier <maz@kernel.org>,
        Oliver Upton <oliver.upton@linux.dev>,
        Huacai Chen <chenhuacai@kernel.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Anup Patel <anup@brainfault.org>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Christian Brauner <brauner@kernel.org>,
        "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>, kvm@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev,
        linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org,
        linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, Xiaoyao Li <xiaoyao.li@intel.com>,
        Xu Yilun <yilun.xu@intel.com>,
        Chao Peng <chao.p.peng@linux.intel.com>,
        Fuad Tabba <tabba@google.com>,
        Jarkko Sakkinen <jarkko@kernel.org>,
        Anish Moorthy <amoorthy@google.com>,
        Yu Zhang <yu.c.zhang@linux.intel.com>,
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        =?UTF-8?B?TWlja2HDq2wgU2FsYcO8bg==?= <mic@digikod.net>,
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        Ackerley Tng <ackerleytng@google.com>,
        Maciej Szmigiero <mail@maciej.szmigiero.name>,
        David Hildenbrand <david@redhat.com>,
        Quentin Perret <qperret@google.com>,
        Michael Roth <michael.roth@amd.com>,
        Wang <wei.w.wang@intel.com>,
        Liam Merwick <liam.merwick@oracle.com>,
        Isaku Yamahata <isaku.yamahata@gmail.com>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
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On Mon, Oct 30, 2023 at 10:01=E2=80=AFAM Paolo Bonzini <pbonzini@redhat.com=
> wrote:
>
> On Mon, Oct 30, 2023 at 5:53=E2=80=AFPM David Matlack <dmatlack@google.co=
m> wrote:
> >
> > On 2023-10-27 11:21 AM, Sean Christopherson wrote:
> > > From: Chao Peng <chao.p.peng@linux.intel.com>
> > >
> > > Currently in mmu_notifier invalidate path, hva range is recorded and
> > > then checked against by mmu_notifier_retry_hva() in the page fault
> > > handling path. However, for the to be introduced private memory, a pa=
ge
> >                           ^^^^^^^^^^^^^^^^^^^^^^^^
> >
> > Is there a missing word here?
>
> No but there could be missing hyphens ("for the to-be-introduced
> private memory"); possibly a "soon" could help parsing and that is
> what you were talking about?

Ah that explains it :)

>
> > >       if (likely(kvm->mmu_invalidate_in_progress =3D=3D 1)) {
> > > +             kvm->mmu_invalidate_range_start =3D INVALID_GPA;
> > > +             kvm->mmu_invalidate_range_end =3D INVALID_GPA;
> >
> > I don't think this is incorrect, but I was a little suprised to see thi=
s
> > here rather than in end() when mmu_invalidate_in_progress decrements to
> > 0.
>
> I think that would be incorrect on the very first start?

Good point. KVM could initialize start/end before registering
notifiers, but that's extra code.