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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 17:07:46 +0000	[thread overview]
Message-ID: <YgP04kJeEH0I+hIw@google.com> (raw)
In-Reply-To: <20220209170020.1775368-1-pbonzini@redhat.com>

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

  parent reply	other threads:[~2022-02-09 17:07 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 ` Sean Christopherson [this message]
2022-02-09 17:11   ` [PATCH 00/12] KVM: MMU: " Paolo Bonzini
2022-02-09 17:16     ` Sean Christopherson

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