Hi,
This patch series implements a lockless access tracking mechanism for KVM
when running on Intel CPUs that do not have EPT A/D bits.
Currently, KVM tracks accesses on these machines by just clearing the PTEs
and then remapping them when they are accessed again. However, the remapping
requires acquiring the MMU lock in order to lookup the information needed to
construct the PTE. On high core count VMs, this can result in significant MMU
lock contention when running some memory-intesive workloads.
This new mechanism just marks the PTEs as not-present, but keeps all the
information within the PTE instead of clearing it. When the page is accessed
again, the PTE can thus be restored without needing to acquire the MMU lock.
Junaid Shahid (4):
kvm: x86: mmu: Use symbolic constants for EPT Violation Exit
Qualifications
kvm: x86: mmu: Rename spte_is_locklessly_modifiable()
kvm: x86: mmu: Fast Page Fault path retries
kvm: x86: mmu: Lockless access tracking for Intel CPUs without EPT A
bits.
arch/x86/include/asm/vmx.h | 55 +++++++
arch/x86/kvm/mmu.c | 399 +++++++++++++++++++++++++++++++++------------
arch/x86/kvm/mmu.h | 2 +
arch/x86/kvm/vmx.c | 40 ++++-
4 files changed, 382 insertions(+), 114 deletions(-)
--
2.8.0.rc3.226.g39d4020
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