[v6,0/4] KVM: arm64: Errata management for VM Live migration

Message

Shameer Kolothum Feb. 5, 2025, 1:22 p.m. UTC

Hi,

v5 --> v6
https://lore.kernel.org/kvmarm/[e-mail]/

-Addressed comments from Oliver,
 -Changed version to 32 bit to match SMCCC_VERSION
 -Don't advertise pKVM hypercalls to guests.
 -Moved hypercall invocation to kvm_guest.c

This can be sanity tested by the Qemu branch here,
https://github.com/hisilicon/qemu/tree/v9.0-nv-rfcv4-vcpu-model-v2-target-cpu-errata
(branch based on Eric's/Connie's NV + custom CPU series)
Eg: to specify target impl CPUs,
-machine virt,.., x-target-impl-cpus=0xMIDR1:0xREVIDR1-0xMIDR2:REVIDR2

Please take a look and let me know your feedback.

Thanks,
Shameer

v4 --> v5
https://lore.kernel.org/kvmarm/[e-mail]/

-Addressed comments from Marc,
 -Added an hypercall to retrieve version and number of supported target
  impl CPUs.
 -Added a check for KVM hypercall services availability.
-Removed R-by tags from Connie & Sebastian as patches 2 & 4 are now
 changed a bit. Please take another look.

v3 --> v4(Minor updates)
https://lore.kernel.org/kvmarm/[e-mail]/

 -Changed MIDR/REVIDR to 64 bits based on feedback from Connie
  and Marc(Patch #3).
 -Added R-by tags from Sebastian (Thanks!).

RFC v2 --> v3
https://lore.kernel.org/kvmarm/[e-mail]/

 -Addressed comments from Oliver(Thanks!).
 -Using implementation CPUs MIDR/REVIDR when it is set for
  _midr_range() functions(Patch 1 & 3)
 -New hypercall for retrieving implementation CPUs(Patch #2).
 -Dropped RFC.

RFC v1 --> RFCv2:
https://lore.kernel.org/kvmarm/[e-mail]/
 -Introduced hypercalls to retrieve target CPUs info from user space VMM.
  see patch #1 for details.
 -Patch #2 uses the hypercall to retrieve the target CPU info if any.
 -Use the target CPUs MIDR/REVIDR in errata enablement. See patch #3.

Background from v1:

On ARM64 platforms most of the errata workarounds are based on CPU
MIDR/REVIDR values and a number of these workarounds need to be
implemented by the Guest kernel as well. This creates a problem when
Guest needs to be migrated to a platform that differs in these
MIDR/REVIDR values even if the VMM can come up with a common minimum
feature list for the Guest using the recently introduced "Writable
ID registers" support.

(This is roughly based on a discussion I had with Marc and Oliver
at KVM forum. Marc outlined his idea for a solution and this is an
attempt to implement it. Thanks to both and I take all the blame
if this is nowhere near what is intended/required)

Shameer Kolothum (4):
  arm64: Modify _midr_range() functions to read MIDR/REVIDR internally
  KVM: arm64: Introduce hypercall support for retrieving target
    implementations
  KVM: arm64: Report all the KVM/arm64-specific hypercalls
  arm64: paravirt: Enable errata based on implementation CPUs

 Documentation/virt/kvm/arm/hypercalls.rst | 59 +++++++++++++++++++++
 arch/arm64/include/asm/cputype.h          | 50 ++++++++++++------
 arch/arm64/include/asm/hypervisor.h       |  1 +
 arch/arm64/include/asm/mmu.h              |  3 +-
 arch/arm64/kernel/cpu_errata.c            | 37 +++++++++----
 arch/arm64/kernel/cpufeature.c            |  8 +--
 arch/arm64/kernel/image-vars.h            |  2 +
 arch/arm64/kernel/proton-pack.c           | 17 +++---
 arch/arm64/kvm/hypercalls.c               |  6 ++-
 arch/arm64/kvm/vgic/vgic-v3.c             |  2 +-
 drivers/clocksource/arm_arch_timer.c      |  2 +-
 drivers/firmware/smccc/kvm_guest.c        | 63 +++++++++++++++++++++++
 include/linux/arm-smccc.h                 | 15 ++++++
 13 files changed, 223 insertions(+), 42 deletions(-)