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

Sean Christopherson
2021-12-09T06:06:06Z

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(-)

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2.34.1.400.ga245620fadb-goog