[PATCH v15 0/7] MTE support for KVM guest

Steven Price
2021-06-14T09:05:46Z

This series adds support for using the Arm Memory Tagging Extensions
(MTE) in a KVM guest.

I realise there are still open questions[1] around the performance of
this series (the 'big lock', tag_sync_lock, introduced in the first
patch). But there should be no impact on non-MTE workloads and until we
get real MTE-enabled hardware it's hard to know whether there is a need
for something more sophisticated or not. Peter Collingbourne's patch[3]
to clear the tags at page allocation time should hide more of the impact
for non-VM cases. So the remaining concern is around VM startup which
could be effectively serialised through the lock.

Changes since v14[2]:

* Dropped "Handle MTE tags zeroing" patch in favour of Peter's similar
patch[3] (now in arm64 tree).

* Improved documentation following Catalin's review.

[1]: https://lore.kernel.org/r/874ke7z3ng.wl-maz%40kernel.org
[2]: https://lore.kernel.org/r/20210607110816.25762-1-steven.price@arm.com/
[3]: https://lore.kernel.org/r/20210602235230.3928842-4-pcc@google.com/

Steven Price (7):
arm64: mte: Handle race when synchronising tags
arm64: mte: Sync tags for pages where PTE is untagged
KVM: arm64: Introduce MTE VM feature
KVM: arm64: Save/restore MTE registers
KVM: arm64: Expose KVM_ARM_CAP_MTE
KVM: arm64: ioctl to fetch/store tags in a guest
KVM: arm64: Document MTE capability and ioctl

Documentation/virt/kvm/api.rst | 57 +++++++++++++++
arch/arm64/include/asm/kvm_arm.h | 3 +-
arch/arm64/include/asm/kvm_emulate.h | 3 +
arch/arm64/include/asm/kvm_host.h | 12 ++++
arch/arm64/include/asm/kvm_mte.h | 66 +++++++++++++++++
arch/arm64/include/asm/mte-def.h | 1 +
arch/arm64/include/asm/mte.h | 8 ++-
arch/arm64/include/asm/pgtable.h | 22 +++++-
arch/arm64/include/asm/sysreg.h | 3 +-
arch/arm64/include/uapi/asm/kvm.h | 11 +++
arch/arm64/kernel/asm-offsets.c | 2 +
arch/arm64/kernel/mte.c | 54 ++++++++++++--
arch/arm64/kvm/arm.c | 16 +++++
arch/arm64/kvm/guest.c | 82 ++++++++++++++++++++++
arch/arm64/kvm/hyp/entry.S | 7 ++
arch/arm64/kvm/hyp/exception.c | 3 +-
arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 21 ++++++
arch/arm64/kvm/mmu.c | 42 ++++++++++-
arch/arm64/kvm/reset.c | 3 +-
arch/arm64/kvm/sys_regs.c | 32 +++++++--
include/uapi/linux/kvm.h | 2 +
21 files changed, 429 insertions(+), 21 deletions(-)
create mode 100644 arch/arm64/include/asm/kvm_mte.h