[PATCH v3 00/21] Track shared pages at EL2 in protected mode

Quentin Perret
2021-07-29T13:28:26Z

Hi all,

This is v3 of the patch series previously posted here:

https://lore.kernel.org/kvmarm/20210726092905.2198501-1-qperret@google.com/

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

Changes since v2:
- Renamed and refactored the find_range() path for host memory aborts;
- Added hyp_assert_lock_held() using Will's hyp_spin_is_locked()
helper, and sprinkled a few of them throughout the series;
- Changed how host stage-2 mappings are adjusted after __pkvm_init() by
walking the hyp stage-1 instead of relying on the host calling
__pkvm_mark_hyp.

Changes since v1:
- Changed the 'share' hypercall to accept a single page at a time;
- Dropped the patch allowing to continue stage-2 map when hitting the
EAGAIN case;
- Dropped some of the custom pgtable walkers and used Marc's get_leaf()
patch instead;
- Changed pgtable API to manipulate SW bits directly rather than
specifying shared pages;
- Added comments and documentations all over;
- Cleanups and small refactoring.

Thanks,
Quentin

Marc Zyngier (1):
KVM: arm64: Introduce helper to retrieve a PTE and its level

Quentin Perret (19):
KVM: arm64: Introduce hyp_assert_lock_held()
KVM: arm64: Provide the host_stage2_try() helper macro
KVM: arm64: Expose page-table helpers
KVM: arm64: Optimize host memory aborts
KVM: arm64: Rename KVM_PTE_LEAF_ATTR_S2_IGNORED
KVM: arm64: Don't overwrite software bits with owner id
KVM: arm64: Tolerate re-creating hyp mappings to set software bits
KVM: arm64: Enable forcing page-level stage-2 mappings
KVM: arm64: Allow populating software bits
KVM: arm64: Add helpers to tag shared pages in SW bits
KVM: arm64: Expose host stage-2 manipulation helpers
KVM: arm64: Expose pkvm_hyp_id
KVM: arm64: Introduce addr_is_memory()
KVM: arm64: Enable retrieving protections attributes of PTEs
KVM: arm64: Mark host bss and rodata section as shared
KVM: arm64: Remove __pkvm_mark_hyp
KVM: arm64: Refactor protected nVHE stage-1 locking
KVM: arm64: Restrict EL2 stage-1 changes in protected mode
KVM: arm64: Make __pkvm_create_mappings static

Will Deacon (1):
KVM: arm64: Add hyp_spin_is_locked() for basic locking assertions at
EL2

arch/arm64/include/asm/kvm_asm.h | 5 +-
arch/arm64/include/asm/kvm_pgtable.h | 166 ++++++++----
arch/arm64/kvm/Kconfig | 9 +
arch/arm64/kvm/arm.c | 46 ----
arch/arm64/kvm/hyp/include/nvhe/mem_protect.h | 33 ++-
arch/arm64/kvm/hyp/include/nvhe/mm.h | 3 +-
arch/arm64/kvm/hyp/include/nvhe/spinlock.h | 25 ++
arch/arm64/kvm/hyp/nvhe/hyp-main.c | 20 +-
arch/arm64/kvm/hyp/nvhe/mem_protect.c | 221 ++++++++++++++--
arch/arm64/kvm/hyp/nvhe/mm.c | 22 +-
arch/arm64/kvm/hyp/nvhe/setup.c | 82 +++++-
arch/arm64/kvm/hyp/pgtable.c | 247 +++++++++---------
arch/arm64/kvm/mmu.c | 28 +-
13 files changed, 625 insertions(+), 282 deletions(-)

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2.32.0.432.gabb21c7263-goog