[PATCH 0/6] KVM ARM64 pre_fault_memory

Jack Thomson
2025-09-11T13:49:38Z

Overview:

This patch series adds ARM64 support for the KVM_PRE_FAULT_MEMORY
feature, which was previously only available on x86 [1]. This allows
a reduction in the number of stage-2 faults during execution. This is
beneficial in post-copy migration scenarios, particularly in memory
intensive applications, where high latencies are experienced due to
the stage-2 faults when pre-populating memory via UFFD / memcpy.

Patch Overview:

- The first patch is a preparatory refactor.

- The second patch is adding a page walk flag for pre-faulting.

- The third patch adds support for the KVM_PRE_FAULT_MEMORY ioctl
on arm64.

- The fourth patch fixes an issue with unaligned mmap allocations
in the selftests.

- The fifth patch updates the pre_fault_memory_test to support
arm64.

- The last patch extends the pre_fault_memory_test to cover
different vm memory backings.

[1]: https://lore.kernel.org/kvm/20240710174031.312055-1-pbonzini@redhat.com

Jack Thomson (6):
KVM: arm64: Add __gmem_abort and __user_mem_abort
KVM: arm64: Add KVM_PGTABLE_WALK_PRE_FAULT walk flag
KVM: arm64: Add pre_fault_memory implementation
KVM: selftests: Fix unaligned mmap allocations
KVM: selftests: Enable pre_fault_memory_test for arm64
KVM: selftests: Add option for different backing in pre-fault tests

arch/arm64/include/asm/kvm_pgtable.h | 3 +
arch/arm64/kvm/Kconfig | 1 +
arch/arm64/kvm/arm.c | 1 +
arch/arm64/kvm/hyp/pgtable.c | 6 +-
arch/arm64/kvm/mmu.c | 97 +++++++++++++--
tools/testing/selftests/kvm/Makefile.kvm | 1 +
tools/testing/selftests/kvm/lib/kvm_util.c | 12 +-
.../selftests/kvm/pre_fault_memory_test.c | 110 +++++++++++++-----
8 files changed, 186 insertions(+), 45 deletions(-)

base-commit: 42188667be387867d2bf763d028654cbad046f7b
--
2.43.0