On Thu, Feb 16, 2023 at 9:12 PM Yu Zhao [off-list ref] wrote:

This patch adds kvm_arch_test_clear_young() for the vast majority of
VMs that are not pKVM and run on hardware that sets the accessed bit
in KVM page tables.

It relies on two techniques, RCU and cmpxchg, to safely test and clear
the accessed bit without taking the MMU lock. The former protects KVM
page tables from being freed while the latter clears the accessed bit
atomically against both the hardware and other software page table
walkers.

Signed-off-by: Yu Zhao <redacted>
---
 arch/arm64/include/asm/kvm_host.h       |  7 +++
 arch/arm64/include/asm/kvm_pgtable.h    |  8 +++
 arch/arm64/include/asm/stage2_pgtable.h | 43 ++++++++++++++
 arch/arm64/kvm/arm.c                    |  1 +
 arch/arm64/kvm/hyp/pgtable.c            | 51 ++--------------
 arch/arm64/kvm/mmu.c                    | 77 ++++++++++++++++++++++++-
 6 files changed, 141 insertions(+), 46 deletions(-)

Adding Marc and Will.

Can you please add other interested parties that I've missed?

Thanks.