From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Ben Gardon <bgardon@google.com>
Subject: [PATCH 00/24] KVM: x86/mmu: Introduce MMU_PRESENT and fix bugs
Date: Thu, 25 Feb 2021 12:47:25 -0800 [thread overview]
Message-ID: <20210225204749.1512652-1-seanjc@google.com> (raw)
This series adds the simple idea of tagging shadow-present SPTEs with
a single bit, instead of looking for non-zero SPTEs that aren't MMIO and
aren't REMOVED. Doing so reduces KVM's code footprint by 2k bytes on
x86-64, and presumably adds a tiny performance boost in related paths.
But, actually adding MMU_PRESENT without breaking one flow or another is
a bit of a debacle. The main issue is that EPT doesn't have many low
available bits, and PAE doesn't have any high available bits. And, the
existing MMU_WRITABLE and HOST_WRITABLE flags aren't optional, i.e. are
needed for all flavors of paging. The solution I settled on is to let
make the *_WRITABLE bit configurable so that EPT can use high available
bits.
Of course, I forgot the above PAE restriction multiple times, and
journeyed down several dead ends. The most notable failed idea was
using the AD_* masks in bits 52 and 53 to denote shadow-present SPTEs.
That would have been quite clever as it would provide the same benefits
without burning another available bit.
Along the many failed attempts, I collected a variety of bug fixes and
cleanups, mostly things found by inspection after doing a deep dive to
figure out what I broke.
Sean Christopherson (24):
KVM: x86/mmu: Set SPTE_AD_WRPROT_ONLY_MASK if and only if PML is
enabled
KVM: x86/mmu: Check for shadow-present SPTE before querying A/D status
KVM: x86/mmu: Bail from fast_page_fault() if SPTE is not
shadow-present
KVM: x86/mmu: Disable MMIO caching if MMIO value collides with L1TF
KVM: x86/mmu: Retry page faults that hit an invalid memslot
KVM: x86/mmu: Don't install bogus MMIO SPTEs if MMIO caching is
disabled
KVM: x86/mmu: Handle MMIO SPTEs directly in mmu_set_spte()
KVM: x86/mmu: Drop redundant trace_kvm_mmu_set_spte() in the TDP MMU
KVM: x86/mmu: Rename 'mask' to 'spte' in MMIO SPTE helpers
KVM: x86/mmu: Stop using software available bits to denote MMIO SPTEs
KVM: x86/mmu: Add module param to disable MMIO caching (for testing)
KVM: x86/mmu: Rename and document A/D scheme for TDP SPTEs
KVM: x86/mmu: Use MMIO SPTE bits 53 and 52 for the MMIO generation
KVM: x86/mmu: Document dependency bewteen TDP A/D type and saved bits
KVM: x86/mmu: Move initial kvm_mmu_set_mask_ptes() call into MMU
proper
KVM: x86/mmu: Co-locate code for setting various SPTE masks
KVM: x86/mmu: Move logic for setting SPTE masks for EPT into the MMU
proper
KVM: x86/mmu: Make Host-writable and MMU-writable bit locations
dynamic
KVM: x86/mmu: Use high bits for host/mmu writable masks for EPT SPTEs
KVM: x86/mmu: Use a dedicated bit to track shadow/MMU-present SPTEs
KVM: x86/mmu: Tweak auditing WARN for A/D bits to !PRESENT (was MMIO)
KVM: x86/mmu: Use is_removed_spte() instead of open coded equivalents
KVM: x86/mmu: Use low available bits for removed SPTEs
KVM: x86/mmu: Dump reserved bits if they're detected on non-MMIO SPTE
Documentation/virt/kvm/locking.rst | 49 +++++----
arch/x86/include/asm/kvm_host.h | 3 -
arch/x86/kvm/mmu.h | 15 +--
arch/x86/kvm/mmu/mmu.c | 87 +++++++---------
arch/x86/kvm/mmu/mmu_internal.h | 16 +--
arch/x86/kvm/mmu/paging_tmpl.h | 2 +-
arch/x86/kvm/mmu/spte.c | 157 ++++++++++++++++++++---------
arch/x86/kvm/mmu/spte.h | 135 +++++++++++++++++--------
arch/x86/kvm/mmu/tdp_mmu.c | 22 ++--
arch/x86/kvm/svm/svm.c | 2 +-
arch/x86/kvm/vmx/vmx.c | 24 +----
arch/x86/kvm/x86.c | 3 -
12 files changed, 290 insertions(+), 225 deletions(-)
--
2.30.1.766.gb4fecdf3b7-goog
next reply other threads:[~2021-02-25 20:48 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-25 20:47 Sean Christopherson [this message]
2021-02-25 20:47 ` [PATCH 01/24] KVM: x86/mmu: Set SPTE_AD_WRPROT_ONLY_MASK if and only if PML is enabled Sean Christopherson
2021-02-25 20:47 ` [PATCH 02/24] KVM: x86/mmu: Check for shadow-present SPTE before querying A/D status Sean Christopherson
2021-02-25 20:47 ` [PATCH 03/24] KVM: x86/mmu: Bail from fast_page_fault() if SPTE is not shadow-present Sean Christopherson
2021-02-25 20:47 ` [PATCH 04/24] KVM: x86/mmu: Disable MMIO caching if MMIO value collides with L1TF Sean Christopherson
2021-02-25 20:47 ` [PATCH 05/24] KVM: x86/mmu: Retry page faults that hit an invalid memslot Sean Christopherson
2021-02-25 20:47 ` [PATCH 06/24] KVM: x86/mmu: Don't install bogus MMIO SPTEs if MMIO caching is disabled Sean Christopherson
2021-02-25 20:47 ` [PATCH 07/24] KVM: x86/mmu: Handle MMIO SPTEs directly in mmu_set_spte() Sean Christopherson
2021-02-25 20:47 ` [PATCH 08/24] KVM: x86/mmu: Drop redundant trace_kvm_mmu_set_spte() in the TDP MMU Sean Christopherson
2021-02-25 20:47 ` [PATCH 09/24] KVM: x86/mmu: Rename 'mask' to 'spte' in MMIO SPTE helpers Sean Christopherson
2021-02-25 20:47 ` [PATCH 10/24] KVM: x86/mmu: Stop using software available bits to denote MMIO SPTEs Sean Christopherson
2021-02-25 20:47 ` [PATCH 11/24] KVM: x86/mmu: Add module param to disable MMIO caching (for testing) Sean Christopherson
2021-02-25 20:47 ` [PATCH 12/24] KVM: x86/mmu: Rename and document A/D scheme for TDP SPTEs Sean Christopherson
2021-02-25 20:47 ` [PATCH 13/24] KVM: x86/mmu: Use MMIO SPTE bits 53 and 52 for the MMIO generation Sean Christopherson
2021-02-25 20:47 ` [PATCH 14/24] KVM: x86/mmu: Document dependency bewteen TDP A/D type and saved bits Sean Christopherson
2021-02-25 20:47 ` [PATCH 15/24] KVM: x86/mmu: Move initial kvm_mmu_set_mask_ptes() call into MMU proper Sean Christopherson
2021-02-25 20:47 ` [PATCH 16/24] KVM: x86/mmu: Co-locate code for setting various SPTE masks Sean Christopherson
2021-02-25 20:47 ` [PATCH 17/24] KVM: x86/mmu: Move logic for setting SPTE masks for EPT into the MMU proper Sean Christopherson
2021-02-25 20:47 ` [PATCH 18/24] KVM: x86/mmu: Make Host-writable and MMU-writable bit locations dynamic Sean Christopherson
2021-02-25 20:47 ` [PATCH 19/24] KVM: x86/mmu: Use high bits for host/mmu writable masks for EPT SPTEs Sean Christopherson
2021-02-25 20:47 ` [PATCH 20/24] KVM: x86/mmu: Use a dedicated bit to track shadow/MMU-present SPTEs Sean Christopherson
2021-03-08 18:52 ` Tom Lendacky
2021-03-08 19:48 ` Paolo Bonzini
2021-03-08 20:11 ` Sean Christopherson
2021-03-08 21:49 ` Sean Christopherson
2021-02-25 20:47 ` [PATCH 21/24] KVM: x86/mmu: Tweak auditing WARN for A/D bits to !PRESENT (was MMIO) Sean Christopherson
2021-05-06 23:05 ` Matteo Croce
2021-05-07 7:38 ` Paolo Bonzini
2021-02-25 20:47 ` [PATCH 22/24] KVM: x86/mmu: Use is_removed_spte() instead of open coded equivalents Sean Christopherson
2021-02-25 20:47 ` [PATCH 23/24] KVM: x86/mmu: Use low available bits for removed SPTEs Sean Christopherson
2021-02-25 20:47 ` [PATCH 24/24] KVM: x86/mmu: Dump reserved bits if they're detected on non-MMIO SPTE Sean Christopherson
2021-02-26 9:38 ` [PATCH 00/24] KVM: x86/mmu: Introduce MMU_PRESENT and fix bugs Paolo Bonzini
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