linux-kernel - Re: [PATCH v13 03/35] KVM: Use gfn instead of hva for mmu_notifier

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CABgObfYM4nyb1K3xJVGvV+eQmZoLPAmz2-=1CG8++pCwvVW7Qg@mail.gmail.com>
Date:   Mon, 30 Oct 2023 18:00:49 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     David Matlack <dmatlack@...gle.com>
Cc:     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>, 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>,
        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 03/35] KVM: Use gfn instead of hva for mmu_notifier_retry

On Mon, Oct 30, 2023 at 5:53 PM David Matlack <dmatlack@...gle.com> wrote:
>
> On 2023-10-27 11:21 AM, Sean Christopherson wrote:
> > From: Chao Peng <chao.p.peng@...ux.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 page
>                           ^^^^^^^^^^^^^^^^^^^^^^^^
>
> 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?

> >       if (likely(kvm->mmu_invalidate_in_progress == 1)) {
> > +             kvm->mmu_invalidate_range_start = INVALID_GPA;
> > +             kvm->mmu_invalidate_range_end = INVALID_GPA;
>
> I don't think this is incorrect, but I was a little suprised to see this
> here rather than in end() when mmu_invalidate_in_progress decrements to
> 0.

I think that would be incorrect on the very first start?

> > +     }
> > +}
> > +
> > +void kvm_mmu_invalidate_range_add(struct kvm *kvm, gfn_t start, gfn_t end)
> > +{
> > +     lockdep_assert_held_write(&kvm->mmu_lock);
>
> Does this compile/function on KVM architectures with
> !KVM_HAVE_MMU_RWLOCK?

Yes:

#define lockdep_assert_held_write(l)    \
        lockdep_assert(lockdep_is_held_type(l, 0))

where 0 is the lock-held type used by lock_acquire_exclusive. In turn
is what you get for a spinlock or mutex, in addition to a rwlock or
rwsem that is taken for write.

Instead, lockdep_assert_held() asserts that the lock is taken without
asserting a particular lock-held type.

> > @@ -834,6 +851,12 @@ void kvm_mmu_invalidate_end(struct kvm *kvm, unsigned long start,
>
> Let's add a lockdep_assert_held_write(&kvm->mmu_lock) here too while
> we're at it?

Yes, good idea.

Paolo