linux-kernel - Re: [PATCH v10 5/9] KVM: Use gfn instead of hva for mmu_notifier

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Date:   Fri, 9 Dec 2022 14:24:31 +0800
From:   Chao Peng <chao.p.peng@...ux.intel.com>
To:     Fuad Tabba <tabba@...gle.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
        linux-doc@...r.kernel.org, qemu-devel@...gnu.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Sean Christopherson <seanjc@...gle.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>,
        Arnd Bergmann <arnd@...db.de>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        Miaohe Lin <linmiaohe@...wei.com>, x86@...nel.org,
        "H . Peter Anvin" <hpa@...or.com>, Hugh Dickins <hughd@...gle.com>,
        Jeff Layton <jlayton@...nel.org>,
        "J . Bruce Fields" <bfields@...ldses.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Shuah Khan <shuah@...nel.org>, Mike Rapoport <rppt@...nel.org>,
        Steven Price <steven.price@....com>,
        "Maciej S . Szmigiero" <mail@...iej.szmigiero.name>,
        Vlastimil Babka <vbabka@...e.cz>,
        Vishal Annapurve <vannapurve@...gle.com>,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        luto@...nel.org, jun.nakajima@...el.com, dave.hansen@...el.com,
        ak@...ux.intel.com, david@...hat.com, aarcange@...hat.com,
        ddutile@...hat.com, dhildenb@...hat.com,
        Quentin Perret <qperret@...gle.com>,
        Michael Roth <michael.roth@....com>, mhocko@...e.com,
        wei.w.wang@...el.com
Subject: Re: [PATCH v10 5/9] KVM: Use gfn instead of hva for
 mmu_notifier_retry

On Tue, Dec 06, 2022 at 03:48:50PM +0000, Fuad Tabba wrote:
...
 > >
> > > >          */
> > > > -       if (unlikely(kvm->mmu_invalidate_in_progress) &&
> > > > -           hva >= kvm->mmu_invalidate_range_start &&
> > > > -           hva < kvm->mmu_invalidate_range_end)
> > > > -               return 1;
> > > > +       if (unlikely(kvm->mmu_invalidate_in_progress)) {
> > > > +               /*
> > > > +                * Dropping mmu_lock after bumping mmu_invalidate_in_progress
> > > > +                * but before updating the range is a KVM bug.
> > > > +                */
> > > > +               if (WARN_ON_ONCE(kvm->mmu_invalidate_range_start == INVALID_GPA ||
> > > > +                                kvm->mmu_invalidate_range_end == INVALID_GPA))
> > >
> > > INVALID_GPA is an x86-specific define in
> > > arch/x86/include/asm/kvm_host.h, so this doesn't build on other
> > > architectures. The obvious fix is to move it to
> > > include/linux/kvm_host.h.
> >
> > Hmm, INVALID_GPA is defined as ZERO for x86, not 100% confident this is
> > correct choice for other architectures, but after search it has not been
> > used for other architectures, so should be safe to make it common.

As Yu posted a patch:
https://lore.kernel.org/all/20221209023622.274715-1-yu.c.zhang@linux.intel.com/

There is a GPA_INVALID in include/linux/kvm_types.h and I see ARM has already
been using it so sounds that is exactly what I need.

Chao
> 
> With this fixed,
> 
> Reviewed-by: Fuad Tabba <tabba@...gle.com>
> And the necessary work to port to arm64 (on qemu/arm64):
> Tested-by: Fuad Tabba <tabba@...gle.com>
> 
> Cheers,
> /fuad