[PATCH v3 0/2] KVM: arm64: Stop stage-2 teardown scaling with the IPA size

[Fuad Tabba <fuad.tabba@linux.dev>]

Hi folks,

Changes since v2 [1]:
  - Return a failed walk's error to the callers and warn there, instead
    of inside the walk. (Oliver)
  - Dropped the comment on the next-mapping lookup. (Vincent)
  - Collected Reviewed-by from Vincent on patch 2. (thanks!)

Two patches that make stage-2 teardown take time proportional to what
is mapped, rather than to the size of the IPA space as it has since
4ddfab5436b6.

Under QEMU TCG ('-cpu max', 16K pages with LPA2), destroying even an
empty VM takes about 7 seconds in pKVM. Without pKVM it takes about 19
seconds if the VM requests a 52-bit IPA (crosvm requests the host's
limit). With the series, both take well under a second. Tested only
under QEMU.

The first has the page-table walk return where it stopped, so that the
teardown steps over an invalid entry larger than a block-sized chunk in
one go. The second has pKVM return where its next mapping starts.

Based on Linux 7.4-rc1 (6628e7d4c6b25).

Cheers,
/fuad

[1] https://lore.kernel.org/all/20261104124451.2148724-1-fuad.tabba@linux.dev/

Fuad Tabba (2):
  KVM: arm64: Resume stage-2 teardown where the walk stopped
  KVM: arm64: Resume a pKVM stage-2 teardown at the next mapping

 arch/arm64/include/asm/kvm_pgtable.h |  8 ++++++--
 arch/arm64/include/asm/kvm_pkvm.h    |  4 ++--
 arch/arm64/kvm/hyp/pgtable.c         | 19 +++++++++++++++----
 arch/arm64/kvm/mmu.c                 |  6 ++++--
 arch/arm64/kvm/pkvm.c                | 11 ++++++++---
 5 files changed, 35 insertions(+), 13 deletions(-)


base-commit: 6628e7d4c6b25c8d18f1345e3a20d21829aae7e4
-- 
2.47.3