From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
vkuznets@redhat.com, mlevitsk@redhat.com, dmatlack@google.com
Subject: Re: [PATCH 00/12] KVM: MMU: do not unload MMU roots on all role changes
Date: Wed, 9 Feb 2022 17:16:08 +0000 [thread overview]
Message-ID: <YgP22CSj7GHYslYa@google.com> (raw)
In-Reply-To: <fc3a4cdc-5a88-55a9-cfcc-fb7936484cc8@redhat.com>
On Wed, Feb 09, 2022, Paolo Bonzini wrote:
> On 2/9/22 18:07, Sean Christopherson wrote:
> > On Wed, Feb 09, 2022, Paolo Bonzini wrote:
> > > The TDP MMU has a performance regression compared to the legacy MMU
> > > when CR0 changes often. This was reported for the grsecurity kernel,
> > > which uses CR0.WP to implement kernel W^X. In that case, each change to
> > > CR0.WP unloads the MMU and causes a lot of unnecessary work. When running
> > > nested, this can even cause the L1 to hardly make progress, as the L0
> > > hypervisor it is overwhelmed by the amount of MMU work that is needed.
> >
> > FWIW, my flushing/zapping series fixes this by doing the teardown in an async
> > worker. There's even a selftest for this exact case :-)
> >
> > https://lore.kernel.org/all/20211223222318.1039223-1-seanjc@google.com
>
> I'll check it out (it's next on my list as soon as I finally push
> kvm/{master,next}, which in turn was blocked by this work).
No rush, I need to spin a new version (rebase, and hopefully drop unnecessarily
complex be3havior).
> But not zapping the roots is even better
No argument there :-)
prev parent reply other threads:[~2022-02-09 17:16 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-09 17:00 [PATCH 00/12] KVM: MMU: do not unload MMU roots on all role changes Paolo Bonzini
2022-02-09 17:00 ` [PATCH 01/12] KVM: x86: host-initiated EFER.LME write affects the MMU Paolo Bonzini
2022-02-10 22:49 ` Sean Christopherson
2022-02-09 17:00 ` [PATCH 02/12] KVM: MMU: move MMU role accessors to header Paolo Bonzini
2022-02-10 23:00 ` Sean Christopherson
2022-02-09 17:00 ` [PATCH 03/12] KVM: x86: do not deliver asynchronous page faults if CR0.PG=0 Paolo Bonzini
2022-02-10 23:10 ` Sean Christopherson
2022-02-10 23:14 ` Sean Christopherson
2022-02-10 23:16 ` Sean Christopherson
2022-02-11 11:16 ` Paolo Bonzini
2022-02-09 17:00 ` [PATCH 04/12] KVM: MMU: WARN if PAE roots linger after kvm_mmu_unload Paolo Bonzini
2022-02-10 23:20 ` Sean Christopherson
2022-02-11 11:18 ` Paolo Bonzini
2022-02-09 17:00 ` [PATCH 05/12] KVM: MMU: avoid NULL-pointer dereference on page freeing bugs Paolo Bonzini
2022-02-11 0:24 ` Sean Christopherson
2022-02-11 11:21 ` Paolo Bonzini
2022-02-09 17:00 ` [PATCH 06/12] KVM: MMU: rename kvm_mmu_reload Paolo Bonzini
2022-02-11 0:27 ` Sean Christopherson
2022-02-11 10:07 ` Paolo Bonzini
2022-02-11 16:16 ` Sean Christopherson
2022-02-11 16:52 ` Paolo Bonzini
2022-02-09 17:00 ` [PATCH 07/12] KVM: x86: use struct kvm_mmu_root_info for mmu->root Paolo Bonzini
2022-02-11 17:39 ` Sean Christopherson
2022-02-09 17:00 ` [PATCH 08/12] KVM: MMU: do not consult levels when freeing roots Paolo Bonzini
2022-02-11 0:41 ` Sean Christopherson
2022-02-11 0:54 ` Sean Christopherson
2022-02-11 1:07 ` Paolo Bonzini
2022-02-11 1:35 ` Sean Christopherson
2022-02-11 1:44 ` Sean Christopherson
2022-02-11 2:20 ` Sean Christopherson
2022-02-09 17:00 ` [PATCH 09/12] KVM: MMU: look for a cached PGD when going from 32-bit to 64-bit Paolo Bonzini
2022-02-11 1:32 ` Sean Christopherson
2022-02-11 1:37 ` Sean Christopherson
2022-02-11 10:09 ` Paolo Bonzini
2022-02-11 11:45 ` Paolo Bonzini
2022-02-11 17:38 ` Sean Christopherson
2022-02-09 17:00 ` [PATCH 10/12] KVM: MMU: load new PGD after the shadow MMU is initialized Paolo Bonzini
2022-02-11 17:45 ` Sean Christopherson
2022-02-11 17:47 ` Paolo Bonzini
2022-02-09 17:00 ` [PATCH 11/12] KVM: MMU: remove kvm_mmu_calc_root_page_role Paolo Bonzini
2022-02-11 17:53 ` Sean Christopherson
2022-02-09 17:00 ` [PATCH 12/12] KVM: x86: do not unload MMU roots on all role changes Paolo Bonzini
2022-02-11 9:08 ` Nikunj A. Dadhania
2022-02-11 18:48 ` Sean Christopherson
2022-02-14 16:34 ` Paolo Bonzini
2022-02-14 19:24 ` Sean Christopherson
2022-02-15 8:17 ` Paolo Bonzini
2022-02-09 17:07 ` [PATCH 00/12] KVM: MMU: " Sean Christopherson
2022-02-09 17:11 ` Paolo Bonzini
2022-02-09 17:16 ` Sean Christopherson [this message]
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