linux-kernel - Re: [PATCH v3 0/2] KVM: x86/mmu: Skip mmu

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Message-ID: <CAD=HUj5sKKnckSqBjjR8paGegLfSujk03C5uDwzfh=PAaj5BZA@mail.gmail.com>
Date:   Fri, 5 Feb 2021 14:58:38 +0900
From:   David Stevens <stevensd@...omium.org>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     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>, kvm@...r.kernel.org,
        open list <linux-kernel@...r.kernel.org>,
        Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        Huacai Chen <chenhuacai@...nel.org>,
        Aleksandar Markovic <aleksandar.qemu.devel@...il.com>,
        linux-mips@...r.kernel.org, Paul Mackerras <paulus@...abs.org>,
        kvm-ppc@...r.kernel.org,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        David Hildenbrand <david@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        David Stevens <stevensd@...gle.com>
Subject: Re: [PATCH v3 0/2] KVM: x86/mmu: Skip mmu_notifier changes when possible

These patches might be responsible for some instability in one of our
stress tests. I'll send an update once I figure out what's going on.

Thanks,
David

On Thu, Jan 28, 2021 at 9:48 PM Paolo Bonzini <pbonzini@...hat.com> wrote:
>
> On 28/01/21 07:05, David Stevens wrote:
> > These patches reduce how often mmu_notifier updates block guest page
> > faults. The primary benefit of this is the reduction in the likelihood
> > of extreme latency when handling a page fault due to another thread
> > having been preempted while modifying host virtual addresses.
> >
> > v2 -> v3:
> >   - Added patch to skip check for MMIO page faults
> >   - Style changes
> >
> > David Stevens (1):
> >    KVM: x86/mmu: Consider the hva in mmu_notifier retry
> >
> > Sean Christopherson (1):
> >    KVM: x86/mmu: Skip mmu_notifier check when handling MMIO page fault
> >
> >   arch/powerpc/kvm/book3s_64_mmu_hv.c    |  2 +-
> >   arch/powerpc/kvm/book3s_64_mmu_radix.c |  2 +-
> >   arch/x86/kvm/mmu/mmu.c                 | 16 ++++++++------
> >   arch/x86/kvm/mmu/paging_tmpl.h         |  7 ++++---
> >   include/linux/kvm_host.h               | 25 +++++++++++++++++++++-
> >   virt/kvm/kvm_main.c                    | 29 ++++++++++++++++++++++----
> >   6 files changed, 65 insertions(+), 16 deletions(-)
> >
>
> Queued, thanks.
>
> Paolo
>