[00/14] Track shared pages at EL2 in protected mode

Message

Quentin Perret July 19, 2021, 10:47 a.m. UTC

Hi all,

This series aims to improve how the nVHE hypervisor tracks ownership of memory
pages when running in protected mode ("kvm-arm.mode=protected" on the kernel
command line).

The main issue with the existing ownership tracking code is that it is
completely binary: a page is either owned by an entity (e.g. the host) or not.
However, we'll need something smarter to track shared pages, as is needed for
virtio, or even just host/hypervisor communications.

This series introduces a few changes to the kvm page-table library to allow
annotating shared pages in ignored bits (a.k.a. software bits) of leaf entries,
and makes use of that infrastructure to track all pages that are shared between
the host and the hypervisor. We will obviously want to apply the same treatment
to guest stage-2 page-tables, but that is not really possible to do until EL2
manages them directly, so I'll keep that for another series.

The series is split as follows:

 - patches 01-04 are essentially cleanups and optimizations of existing code
   paths that might be relevant on their own, but also prepare the ground for
   the rest of the series;

 - patches 05-08 introduce support in the page-table library for annotating
   shared pages with software bits;

 - patches 09-14 make use of the previously introduced infrastructure to
   annotate all pages shared between the host and the hypervisor;

The series is based on the latest kvmarm/fixes branch, and has been tested
on AML-S905X-CC (Le Potato) and using various Qemu configurations.

Thanks!
Quentin

Quentin Perret (14):
  KVM: arm64: Provide the host_stage2_try() helper macro
  KVM: arm64: Optimize kvm_pgtable_stage2_find_range()
  KVM: arm64: Continue stage-2 map when re-creating mappings
  KVM: arm64: Rename KVM_PTE_LEAF_ATTR_S2_IGNORED
  KVM: arm64: Don't overwrite ignored bits with owner id
  KVM: arm64: Tolerate re-creating hyp mappings to set ignored bits
  KVM: arm64: Enable forcing page-level stage-2 mappings
  KVM: arm64: Add support for tagging shared pages in page-table
  KVM: arm64: Mark host bss and rodata section as shared
  KVM: arm64: Enable retrieving protections attributes of PTEs
  KVM: arm64: Expose kvm_pte_valid() helper
  KVM: arm64: Refactor pkvm_pgtable locking
  KVM: arm64: Restrict hyp stage-1 manipulation in protected mode
  KVM: arm64: Prevent late calls to __pkvm_create_private_mapping()

 arch/arm64/include/asm/kvm_asm.h              |   2 +-
 arch/arm64/include/asm/kvm_pgtable.h          | 109 ++++++---
 arch/arm64/kvm/hyp/include/nvhe/mem_protect.h |   2 +
 arch/arm64/kvm/hyp/include/nvhe/mm.h          |   3 +-
 arch/arm64/kvm/hyp/nvhe/hyp-main.c            |  17 +-
 arch/arm64/kvm/hyp/nvhe/mem_protect.c         | 156 +++++++++++--
 arch/arm64/kvm/hyp/nvhe/mm.c                  |  20 +-
 arch/arm64/kvm/hyp/nvhe/setup.c               |  52 ++++-
 arch/arm64/kvm/hyp/pgtable.c                  | 219 +++++++++++++-----
 arch/arm64/kvm/mmu.c                          |  14 +-
 10 files changed, 454 insertions(+), 140 deletions(-)