linux-kernel - [PATCH 0/7] KVM: x86/mmu: Obsolete root shadow page fix

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Message-Id: <20211209060552.2956723-1-seanjc@google.com>
Date:   Thu,  9 Dec 2021 06:05:45 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>
Cc:     David Hildenbrand <david@...hat.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        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,
        linux-kernel@...r.kernel.org, Maxim Levitsky <mlevitsk@...hat.com>,
        Ben Gardon <bgardon@...gle.com>,
        Lai Jiangshan <jiangshanlai@...il.com>
Subject: [PATCH 0/7]  KVM: x86/mmu: Obsolete root shadow page fix

Patch 01 fixes a complete braino and lack of testing :-(

The rest of the series is an enhancement to address a performance issue
I encountered when implementing the aforementioned fix.  I wanted to WARN
if KVM_REQ_MMU_LOAD was pending with a valid root shadow page, but it
fired like crazy because the roots in prev_roots have an elevated
root_count and thus can trigger KVM_REQ_MMU_LOAD when the guest zaps a
cached root's corresponding PGD (in the guest).

Patches 2+ haven't been super well tested, I'll beat on 'em more and
holler if anything pops up.

Sean Christopherson (7):
  KVM: x86: Retry page fault if MMU reload is pending and root has no sp
  KVM: x86: Invoke kvm_mmu_unload() directly on CR4.PCIDE change
  KVM: Drop kvm_reload_remote_mmus(), open code request in x86 users
  KVM: x86/mmu: Zap only obsolete roots if a root shadow page is zapped
  KVM: s390: Replace KVM_REQ_MMU_RELOAD usage with arch specific request
  KVM: Drop KVM_REQ_MMU_RELOAD and update vcpu-requests.rst
    documentation
  KVM: WARN if is_unsync_root() is called on a root without a shadow
    page

 Documentation/virt/kvm/vcpu-requests.rst |  7 +-
 arch/s390/include/asm/kvm_host.h         |  2 +
 arch/s390/kvm/kvm-s390.c                 |  8 +-
 arch/s390/kvm/kvm-s390.h                 |  2 +-
 arch/x86/include/asm/kvm_host.h          |  2 +
 arch/x86/kvm/mmu.h                       |  1 +
 arch/x86/kvm/mmu/mmu.c                   | 98 +++++++++++++++++++++---
 arch/x86/kvm/x86.c                       | 15 ++--
 include/linux/kvm_host.h                 |  4 +-
 virt/kvm/kvm_main.c                      |  5 --
 10 files changed, 107 insertions(+), 37 deletions(-)

-- 
2.34.1.400.ga245620fadb-goog